INTERNATIONAL    CHEMICAL    SERIES 
H.  P.  TALBOT,  PH.  D.,  CONSULTING  EDITOR 


TECHNICAL 
GAS  AND  FUEL  ANALYSIS 


McGraw-Hill  BookCompany 


Electrical  World         The  Engineering  and  Mining  Journal 
Engineering  Record  Engineering  News 

Railway  Age  G  aze  tte  American  Machinist 

Signal  E,ngin<?<?r  American  Engineer 

Electric  Railway  Journal  Coal  Age 

Metallurgical  and  Chemical  Engineering  P  o  we r 


TECHNICAL 
GAS  AND  FUEL  ANALYSIS 


BY 


ALFRED  H.  WHITE 

PROFESSOR  OF  CHEMICAL  ENGINEERING,  UNIVERSITY  OF  MICHIGAN 


McGRAW-HILL  BOOK  COMPANY,  INC. 
239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.  C. 

1913 


COPYRIGHT,  1913,  BY  THE 
McGRAW-HiLL  BOOK  COMPANY,  INC, 


THE. MAPLE- PRESS- YORK- PA 


PREFACE 

With  the  increased  demand  for  the  economic  utilization  of 
fuels  has  come  an  increased  necessity  for  accuracy  in  testing 
both  the  raw  fuel  and  the  manner  of  its  utilization.  Our  knowl- 
edge has  recently  been  greatly  extended  by  the  investigations 
conducted  by  the  Committee  on  Calorimetry  of  the  American 
Gas  Institute,  the  International  Photometric  Commission,  the 
Joint  Committee  on  Coal  Analysis  of  the  American  Chemical 
Society  and  the  Society  for  Testing  Materials,  the  Bureau  of 
Mines  and  the  Bureau  of  Standards. 

The  author  has  aimed  to  present  the  conclusions  of  these 
committees  and  also  to  indicate  where  the're  has  been  marked 
dissent  from  them.  He  desires  to  express  his  especial  appre- 
ciation to  Professor  O.  L.  Kowalke  of  the  University  of  Wis- 
consin for  his  courtesy  in  revising  the  chapter  on  Determination 
of  Heating  Value  of  Gas;  to  Professor  S.  W.  Parr  of  the  Uni- 
versity of  Illinois  for  suggestions  on  Calorimetry  and  Chemical 
Analysis  of  Coal;  and  to  Dr.  H.  C.  Dickinson  of  the  Bureau 
of  Standards  for  his  suggestions  on  Calorimetry. 

ANN  ARBOR,  MICHIGAN, 
August,  1913. 


271131 

V 


CONTENTS 

PAGE 
PREFACE    v 

CHAPTER  I 

SAMPLING  AND  STORAGE  OF  GASES 1 

Difficulties  involved — The  problem  of  a  fair  sample — Materials 
for  sampling  tubes — Types  of  sampling  tubes  and  their  use — 
Aspirators — Solubility  of  gases  in  water — Saturating  water  in 
sampling  tanks — Collecting  an  average  sample  representative  of  a 
definite  period — Collecting  a  representative  instantaneous  sample 
— Storing  gas  samples. 

CHAPTER  II 

GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS .      14 

Introduction — General  method — The  gas  burette — Care  of  stop- 
cock— Saturating  the  water  of  the  burette — Drawing  the  sample 
of  gas  into  the  burette — Measuring  a  gas  volume — Calibration 
of  a  gas  burette — Connecting  the  burette  and  pipette — Details 
of  a  simple  gas  analysis — Accuracy  of  the  analysis. 

CHAPTER  III 

ABSORPTION  METHODS  FOR  CARBON  DIOXIDE,  UNSATURATED  HYDRO- 
CARBONS, OXYGEN,  CARBON  MONOXIDE  AND  HYDROGEN  ....  28 
Carbon  dioxide — Unsaturated  hydrocarbons — Oxygen  by  phos- 
phorus— Oxygen  by  alkaline  pyrogallate — Other  reagents  for  oxygen 
— Carbon  monoxide — Absorption  of  hydrogen — General  scheme  of 
analysis. 

CHAPTER  IV 

EXPLOSION  AND  COMBUSTION  METHODS  FOR  HYDROGEN,  METHANE, 

ETHANE  AND  CARBON  MONOXIDE 41 

Available  methods — Apparatus  for  explosion  analysis — Manipula- 
tion in  explosion  analysis — Oxidation  of  nitrogen  as  a  source  of 
error — Accuracy  of  explosion  methods — Hydrogen  by  explosion — 
Hydrogen  and  methane  by  explosion — Carbon  monoxide,  hydrogen 
and  methane  by  explosion — Quiet  combustion  of  a  mixture  of 
oxygen  and  combustible  gas — Fractional  combustion  with  palla- 
dinised  asbestos — Fractional  combustion  with  copper  oxide — 
Nitrogen — Form  of  record  of  gas  analysis. 

vii 


viii  CONTENTS 

CHAPTER  V 

PAGE 

VARIOUS  TYPES  OF  APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS      ...      61 
Introduction — Schlosing  and  Holland's  apparatus — Orsat's  appa- 
ratus— Bunte's  burette — Chollar  tubes. 

CHAPTER  VI 

EXACT  GAS  ANALYSIS 70 

Historical — General  methods — Corrections  for  temperature  and 
pressure — Description  of  gas  burettes — The  bulbed  gas  burette 
for  exact  analysis — Manipulation  of  gas  burette  for  exact  analysis 
— Calibration  of  burette — Absorption  methods  in  exact  igas  analysis 
— Carbon  dioxide — Unsaturated  hydrocarbons — Oxygen — Carbon 
monoxide — Hydrogen — Methane — Nitrogen. 

CHAPTER  VII 

HEATING  VALUE  OF  GAS 87 

Introduction — Continuous  flow  calorimeters — Wet  gas  meters — 
Corrections  for  temperature  and  pressure — Control  of  the  water — 
Measurement  of  temperature — Measurement  of  mass  of  water — 
Junkers'  calorimeter — Preliminaries  of  a  test — Description  of  a 
test — Calculation  of  results — Gross  and  net  heat  values — Accuracy 
of  method — Determination  of  humidity  of  air — Non-continuous 
water  heating  calorimeters — Automatic  and  recording  gas  calori- 
meters— Calculation  of  heating  value  from  chemical  composition. 

CHAPTER  VIII 

CANDLE-POWER  OF  ILLUMINATING  GAS  ..............    113 

Introduction — Method  of  rating  candle-power — The  bar  photo- 
meter— Standard  light — Photometric  units — Standard  candles — 
The  Hefner  lamp — The  Pentane  lamp — Secondary  standards  of 
light — Standard  gas  burners — The  Bunsen  and  Leeson  photometric 
screens — The  Lummer  Brodhun  photometric  screen — The  flicker 
photometer — The,  gas  meter — The  photometer  bench  and  its  equip- 
ment— Details  of  a  test — Illustration  of  calculation — The  photo- 
meter room — Jet  photometers — Accuracy  of  photometric  work. 

CHAPTER  IX 

ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS .    .    .    .    133 

Introduction — The  distribution  of  particles  in  the  cross-section  of 
a  straight  main — Mean  velocity  in  the  cross-section  of  a  gas  main — 
Influence  of  bends  in  a  main — Velocity  of  gas  in  a  sampling  tube — 
The  filtering  medium — Estimation  of  suspended  tar  and  water — 
Electrical  precipitation  of  suspended  particles. 


CONTENTS  ix 

CHAPTER  X 

PAGE 

CHIMNEY  GASES 139 

Introduction — Formation  of  carbon  dioxide — Effect  of  hydrogen 
of  coal  on  composition  of  chimney  gases — Carbon  monoxide  and 
products  of  incomplete  combustion — Volume  of  air  and  of  chimney 
gases — Loss  of  heat  in  chimney  gases — Interpretation  of  analysis 
of  chimney  gases. 

CHAPTER  XI 

PRODUCER  GAS    ....    .    ....-, 149 

Formation  of  producer  gas — Sampling  producer  gas — Analysis 
of  producer  gas — Interpretation  of  analysis — Heating  value  of 
producer  gas — Volume  of  producer  gas — Efficiency  of  a  gas 
producer. 

CHAPTER  XII 

ILLUMINATING  GAS  AND  NATURAL  GAS 156 

Introduction — Sampling^General  scheme  of  analysis — Chemical 
composition  of  illuminating  gas — Benzene — Hydrogen  sulphide — 
Total  sulphur  compounds — Napthalene — Ammonia — Cyanogen — 
Specific  gravity — Natural  gas. 

CHAPTER  XIII 

LIQUID  FUELS .„' 174 

Introduction — Sampling — Heating  value — Specific  gravity — Mois- 
ture— Proximate  analysis — Suspended  solids — Flash  point. 

CHAPTER  XIV 

SAMPLING  COAL 181 

General  consideration — A  scoopful  as  a  sample — Influence  of 
lumps  of  slate — Taking  a  sample — Mine  sampling — Preparation 
of  sample — Preservation  of  sample — Usual  accuracy  of  sampling — 
Reliability  of  samples. 

CHAPTER  XV 

THE  CHEMICAL  ANALYSIS  OF  COAL 193 

Introduction — Proximate  analysis — Preliminary  examination  of 
sample — Air-drying — Grinding  and  preserving  the  sample  for 
analysis — Moisture — Volatile  matter — Ash — Fixed  carbon — Sul- 
phur— Ultimate  analysis — Carbon  and  hydrogen — Nitrogen — 
Phosphorus — Oxygen — Methods  of  reporting  analyses — Accu 
of  results — Slate  and  pyrites. 


x  CONTENTS 

CHAPTER  XVI 

PAGE 

HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER 214 

General  methods  of  determining  heating  value — The  bomb  calori- 
meter— Details  of  the  bomb  calorimeter — Thermometers — Prepa- 
ration of  sample — Manipulation  of«  bomb  calorimeter — Thermom- 
eter corrections — Radiation  corrections — Corrections  for  oxida- 
tion of  nitrogen — Corrections  due  to  oxidation  of  sulphur — 
Correction  due  to  combustion  of  iron  wire — Reduction  to  constant 
pressure — Water  value  of  calorimeter — Accuracy  of  results — 
Gross  and  net  heating  values. 

CHAPTER  XVII 

HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER  AND  OTHER 

METHODS 238 

Introduction — Combustion  in  a  stream  of  oxygen — The  Thompson 
calorimeter — The  Parr  calorimeter — Preparation  of  Parr  calori- 
meter— Care  of  sodium  peroxide — Operation  of  Parr  calorimeter — 
Corrections  to  be  applied  with  Parr  calorimeter — Accuracy  of  Parr 
calorimeter — Calculation  of  heating  value  from  chemical  analysis. 

INDEX     .    .  .   257 


TECHNICAL 
GAS  AND  FUEL  ANALYSIS 

CHAPTER  I 
SAMPLING  AND  STORAGE  OF  GASES 

1.  Difficulties  Involved. — The  problem  of  obtaining  a  repre- 
sentative sample  of  a  gas  for  analysis  presents  in  many  cases 
more  difficulties  than  the  analysis  itself.     If  the  gas  flowing 
through  a  main  were  of  perfectly  uniform  composition  throughout 
its  cross-section  and  also  throughout  its  length  the  problem  would 
simplify  itself  to  the  introduction  of  a  tube  through  which  a  por- 
tion of  gas  might  be  removed  for  analysis.     The  proposition 
becomes  at  once  more  complicated  when  it  is  necessary  to  sample 
gases  which  have  not  passed  through  any  adequate  mixing  chamber 
and  which  usually  travel  through  the  main  or  flue  in  pulsations 
of  widely  varying  composition.     Ocular  evidence  of  this  condition 
is  afforded  by  a  glance  at  the  average  smoke  stack  with  its  pulsing 
billows  of  smoke.     If  it  is  desired  to  determine  not  only  the  com- 
position of  the  fixed  gases  but  also  the  amounts  of  suspended 
solids,  tar  particles,  water  globules,  etc.,  the  problem  becomes 
one   of  great  complexity,   capable    frequently  of    only  partial 
solution.     This  question  is  discussed  separately  in  Chapter  IX. 

2.  The  Problem  of  a  Fair  Sample. — Gases  should  be  sampled 
as  close  as  possible  to  the  point  of  the  reactions  which  are  to  be 
studied,  thus  minimizing  errors  due  to  leakage  of  air  or  gas, 
deposition  of  solids  or  secondary  reactions.     Gases  travel  through 
straight  pipes  in  an  irregular  succession  of  waves  of  rather  a 
spiral  form,  the  velocity  being  greatest  at  the  center  of  the  pipe 
and  least  next  to  the  walls.     The  shape  of  the  wave  is  altered  by 
every  bend,  branch  or  other  change  in  the  pipe  and  the  point  of 
maximum  velocity  is  also  shifted.     The  temperature  of  gases 
from  hot  furnaces  also  varies  throughout  the  cross-section  of  the 

1 


2  GAs  'AND  FUEL  ANALYSIS 

conducting  pipe!, '  freiiig  usually  hottest  where  the  velocity  is 
greatest  and  coldest  next  to  the  walls  and  in  dead  bends. 

It  is  in  general  advisable  to  sample  from  a  point  of  approxi- 
mately average  velocity  and  temperature,  but  it  is  not  possible  to 
find  a  single  point  from  which  a  truly  representative  instantaneous 
sample  can  be  drawn.  It  is  necessary  to  extend  the  sampling 
period  over  a  time  which  will  on  the  theory  of  probabilities  allow 
so  great  a  series  of  gas  waves  to  pass  the  sampling  tube  that  the 
resulting  sample  will  be  truly  representative.  A  small  volume  of 
gas  can  therefore  only  be  considered  a  representative  sample 
when  it  has  been  drawn  from  a  practically  homogeneous  mass  of 
gas — a  condition  which  is  rather  closely  fulfilled  in  illuminating 
gas  which  has  been  purified  and  further  made  uniform  through 
mixing  and  diffusion  in  a  large  gas  holder.  The  condition  is  not 
fulfilled  in  producer  or  chimney  gases. 

No  fixed  time  can  be  set  as  the  most  desirable  for  a  single  gas 
sample.  If  the  sample  is  being  taken  from  chimney  gases  which 
are  supposed  to  be  the  same  from  one  hour  to  another,  the  sam- 
pling process  may  very  well  extend  over  one  hour  or  six  hours. 
The  longer  the  period  the  more  nearly  will  the  sample  be  an 
average  one.  The  same  thing  holds  true  for  illuminating  gas 
coming  from  a  holder,  but  it  would  not  hold  true  for  producer  gas 
from  a  single  producer  nor  for  illuminating  gas  from  a  single  re- 
tort, for  these  gases  vary  continuously  in  composition,  each  fresh 
charge  of  coal  commencing  a  new  cycle.  When  dealing  with  gases 
of  this  sort  it  is  necessary  to  start  and  stop  the  sampling  with  refer- 
ence to  some  definite  point  in  the  cycle.  A  truly  proportional 
sample  of  a  constantly  varying  gas  cannot  be  obtained  without 
rather  elaborate  precautions. 

3.  Materials  for  Sampling  Tubes. — Sampling  tubes  must  be 
of  a  material  which  will  not  react  with  the  gases  and  change 
their  chemical  composition.  Iron,  and  in  general  metals,  cannot 
be  used  at  high  temperatures.  Iron  reacts  with  carbon  dioxide 
quite  rapidly  at  400°  F.,  producing  carbon  monoxide  and  oxide 
of  iron.  It  also  reacts  readily  with  oxygen.  An  oxidized  pipe 
will  react  with  hydrogen  causing  that  gas  to  disappear  as  water 
at  equally  low  temperatures.  Pipes  with  rough  surface  will 
induce  a  rapid  catalytic  decomposition  of  such  gases  as  ammonia 
and  some  of  the  less  stable  hydrocarbons  at  a  rather  low  red  heat, 


SAMPLING  AND  STORAGE  OF  GASES  3 

The  best  materials  for  sampling  tubes  are  glass,  quartz  or 
porcelain.  These  tubes  should  be  protected  by  a  wrapping  of 
asbestos  in  the  form  of  paper  or  twine  and  should  be  slipped  into 
an  iron  jacket  which  takes  the  strain  off  the  tube  and  prevents 
sudden  temperature  changes.  Glass  begins  to  soften  about 
600°  C.  or  1100°  F.  and  on  long  exposure  to  a  red  heat  devitrifies 
and  ultimately  cracks  spontaneously  on  cooling.  Porcelain  will 
stand  about  1000°  C.  or  a  little  over  1800°  F.,  but  at  higher 
temperatures  the  glaze  commences  to  soften.  Unglazed  porcelain 
will  stand  a  higher  temperature  and  special  refractory  mixtures 
may  be  obtained  which  will  not  soften  at  1700°  C.  or  3000°  F., 
but  such  tubes  are  apt  to  be  porous  and  should  only  be  used  if 
proved  to  be  free  from  leaks.  Fused  quartz  is  in  some  respects 
admirable  as  a  material  for  sampling  tubes,  since  its  coefficient  of 
expansion  is  so  small  that  it  never  cracks  because  of  temperature 
changes.  It  will  stand  1100°  C.  or  about  2000°  F.  without 
softening  but  on  long  heating  tends  to  become  crystalline  and 
brittle.  The  ordinary  electroquartz  tubes  are  often  porous  and 
should  be  carefully  tested. 

4.  Types  of  Sampling  Tubes  and  Their  Use. — The  simplest 
form  of  sampling  apparatus  consists  of  a  single  tube  through 
whose  open  end  the  gases  are  aspirated.  When  sampling  from 
a  large  flue  the  sampling  tube  is  sometimes  closed  at  the  end  and 
perforated  at  various  points  along  its  length  with  the  expectation 
that  gas  will  be  drawn  uniformly  through  the  holes  at  intervals 
across  the  flue.  A  device  of  this  sort  usually  fails  of  its  purpose 
and  is  often  less  efficient  than  a  single  tube.  If  the  perforations 
are  all  of  the  same  diameter  they  will  allow  the  same  amount  of 
gas  to  pass  through  only  in  case  the  suction  is  the  same  on 
each.  This  condition  can  be  attained  in  practice  only  by 
making  the  perforations  small  and  the  suction  high  so  that  it 
will  be  practically  as  great  at  the  far  as  at  the  near  end  of  the 
sampling  tube.  But  such  small  holes  stop  quickly  with  dust  and 
are  not  practicable. 

A  better  device  to  secure  a  more  uniform  sample  from  the  gases 
of  a  flue  is  shown  in  Fig.  1.  It  consists  of  a  bundle  of  glass  tubes 
of  the  same  diameter  but  of  varying  lengths  which  are  wired  to- 
gether and  slipped  into  an  iron  pipe  not  quite  so  long  as  the  short- 
est glass  tube.  The  glass  tubes  are  cemented  into  this  with  neat 


4  GAS  AND  FUEL  ANALYSIS 

Portland  cement  in  such  a  manner  that  their  ends  next  the  threaded 
joint  are  all  even  and  about  2  in.  from  the  end  of  the  iron  tube. 
This  may  readily  be  accomplished  in  the  following  manner. 
Plug  the  threaded  end  of  the  iron  pipe  with  a  cork  and  stand  it 
vertically  on  the  corked  end.  Plug  one  end  of  each  of  the  glass 
tubes  with  putty  and  stand  them  in  the  iron  tube  with  their 
lower  ends  resting  on  the  cork.  Fill  the  iron  tube  for  3  in.  with 
a  paste  of  Portland  cement  and  water  and  allow  to  stand  for 
twelve  hours  to  harden.  The  sampler  is  finished  after  removing 
the  cork  and  putty  by  screwing  onto  the  iron  pipe  a  cap  which  is 
provided  with  a  1/4-in.  nipple  to  which  convenient  connection 
may  be  made.  The  suction  required  to  draw  a  slow  stream  of 
gas  through  a  smooth  tube  2  ft.  long  is  only  slightly  more  than 
that  required  for  a  1-ft.  tube.  The  empty  space  at  the  end 
of  the  pipe  acts  as  a  mixing  chamber  and  allows  a  fairly  satis- 
factory sample  to  be  drawn  through  the  nipple. 

The  sampling  tube  is  to  be  inserted  in  the  flue  in  such  a  way 


FIG.  1. — Multiple  gas  sampling  tube. 

that  there  will  be  no  leakage  around  it.  An  iron  gas  main  may 
be  drilled  and  tapped  to  receive  a  threaded  nipple  into  which 
the  sampling  tube  is  luted  when  in  use  and  which  is  closed  by  a 
cap  when  not  in  use.  When  a  hole  must  be  cut  through  a  brick 
wall  a  threaded  nipple  may  be  cemented  permanently  into  the 
wall  and  closed,  when  not  in  use,  with  a  cap.  If  only  a  single 
sampling  tube  is  used  it  should  be  inserted  to  about  the  point  of 
mean  velocity  of  the  gases,  a  subject  which  is  discussed  in  Chapter 
IX.  Where  a  multiple  sampling  tube  of  the  above  type  is  used 
it  should  be  inserted  so  that  the  longest  tube  reaches  at  least  to 
the  center  of  the  flue. 

It  is  frequent  but  bad  practice  to  connect  the  sampling  tube 
and  the  aspirator  by  a  rubber  tube.  Rubber  is  softened  and 
burned  by  hot  gases  and  yields  gaseous  products  which  contami- 
nate the  sample.  It  also  dissolves  tar  and  hydrocarbon  vapors 
and  even  permanent  gases  like  ethylene  in  sufficient  amount  to 
materially  change  the  character  of  the  gas.  Furthermore,  even 


SAMPLING  AND  STORAGE  OF  GASES  5 

the  best  rubber  is  never  gas  tight  but  always  allows  some  leakage. 
It  is  usually  necessary  to  use  a  small  amount  of  rubber  tubing 
in  making  connections,  but  its  use  should  be  restricted  to  lengths 
of  only  an  inch  or  two  where  it  serves  as  a  connector  between  glass 
tubes.  When  thus  used  a  copper  wire  should  be  twisted  tightly 
around  the  rubber  where  it  slips  over  the  glass  tube  to  ensure  a 
tight  joint. 

5.  Aspirators. — The  commonest  form  of  aspirator  consists 
of  a  bottle  or  tank  initially  filled  with  water  which  flows  slowly 
out  and  is  replaced  by  the  gas.  With  this  form  of  aspirator  the 
suction  constantly  decreases  as  the  head  of  water  drops  and  there- 
fore the  flow  of  gas  slackens,  which  is  a  disadvantage.  This 
may  be  overcome  by  making  the  gas  as  it  enters  pass  down 
through  a  central  tube  and  then  bubble  up  through  the  water  on 
the  principle  of  the  Marriotte  bottle,  but  unless  the  water  of  the 
aspirator  has  been  previously  thoroughly  saturated  with  the  gas 
this  process  is  certain  to  change  the  composition  of  the  gas  very 
materially.  The  extent  of  the  error  introduced  by  failure  to 
observe  this  precaution  is  discussed  later.  A  film  of  heavy  par- 
affine  oil  is  sometimes  poured  on  the  water  of  the  aspirator 
bottle  to  prevent  interaction  between  the  water  and  the  gas. 
Such  an  oil-film  does  not,  however,  prevent  the  interaction  and 
does  not  even  make  it  much  slower.  If  oil  is  used  it  should  be  at 
least  as  heavy  as  a  lubricating  oil  so  that  it  will  not  give  off  any 
appreciable  volume  of  vapors  which  even  in  small  amount  will 
cause  difficulty  in  the  estimation  of  oxygen  by  phosphorus. 

011  should  not  be  used  when  the  gases  sampled  contain  hydro- 
carbons, since  these  are  quite  soluble  in  heavy  mineral  oils. 

Where  frequent  samples  are  to  be  drawn  a  pair  of  aspirator 
tanks  as  shown  in  Fig.  2  are  to  be  recommended.  Tanks  to  hold 
approximately  a  cubic  foot  should  have  the  cylindrical  portion 

12  in.  in  diameter  and  12  in.  high  with  the  cones  each  6  in.  high. 
They  may  be  made  of  galvanized  iron  and  will  be  strong  enough 
with  merely  soldered  seams  if  they  are  not  knocked  about  too 
much.     The  ends  of  the  cones  terminate  in  short  1/2-in.  nipples 
soldered  in.     The  lower  end  of  the  tank  carries  screwed  to  this 
nipple  a  1/2-in.  cock  F,  and  beyond  this  another  1/2-in.  nipple 
with  a  hose  union.     The  upper  nipple  carries  a  1/2-in.  tee  on 
whose  side-arm  is  an  ordinary  1/4-in.  gas  cock  E,  and  on  whose 


6  GAS  AND  FUEL  ANALYSIS 

upper  end  is  a  cap  tapped  for  a  1/4-in.  pipe.  This  pipe,  cut  the 
length  of  the  tank,  is  threaded  into  the  cap  from  the  inside  be- 
fore the  latter  is  in  place  so  that  when  screwed  together  the  1/4-in. 
pipe  runs  the  whole  length  of  the  tank  and  projects  through  the 
cap  enough  to  receive  the  gas  cock  D.  With  a  pair  of  bottles 
of  this  sort  the  water  flows  from  one  to  the  other  and  is  not 
exposed  to  the  air  so  that  it  remains  saturated  with  the  gas. 

If  a  water  or  steam  line  is  at  hand  an  inj  ector  may  be  employed 
as  an  aspirator.  It  is  desirable  in  most  cases  to  have  the  suction 
a  slight  and  steady  one,  a  condition  not  readily  attained  with 
injectors  running  only  to  a  small  per  cent,  of  their  capacity.  It  is 
well  to  have  the  injector  open  more  widely  than  is  necessary  to 
furnish  the  suction  required  and  to  have  on  the  line  an  automatic 
water  seal  relief  valve  as  indicated  at  E  in  Fig.  3  which  will  suck 
in  air  at  the  inlet  of  the  aspirator  if  the  suction  rises  too  high. 

6.  Solubility  of  Gases  in  Water. — The  solubility  of  gases  in 
water  varies  with  the  temperature  and  the  pressure.  For  our 
treatment  it  will  be  sufficient  to  assume  that  the  gas  is  always 
under  atmospheric  pressure  and  at  ordinary  room  temperatures. 
Under  these  circumstances  the  solubility  of  the  common  gases  is 
as  follows :  ' 


SOLUBILITY  OF  GASES  IN  WATER 

Expressed  as  the  volume  gas  dissolved  by  unit  volume  water  at  the  tem- 
perature of  the  experiment  when  in  contact  with  the  pure  gas  at  atmos- 
pheric pressure. 


59°  F. 

77°  F. 

Carbon  dioxide       .                                      .  . 

1  070 

0.826 

Oxvscen 

0  036 

0  031 

Nitrogen  

0.019 

0.016 

Carbon  monoxide  

0.027 

0.023 

Methane  .  .       

0  039 

0.033 

Ethvlene.  . 

0.147 

0.119 

When  mixed  gases  are  in  contact  with  water  the  amount  of 
each  gas  dissolved  will  be  in  direct  proportion  to  its  volume  and 
its  solubility.  Thus  the  composition  of  pure  water  saturated 
with  air  at  59°  F.  would  be 


SAMPLING  AND  STORAGE  OF  GASES 


Composition  of 
air,  per  cent. 

Volumes  of  gases  in  100  vols. 
water 

Percentage  com- 
position of  gas 
dissolved  by  water 

CO2  0.04 
O2  21.0 

0.04X1.07    =  0.043  vols.  CO2 
21.0   X  0.036  =0.756  vols.     O2 

1.9 
32.9 

N2      79.0 

79.0   XO  019  =  1  500  vols.     No 

65.2 

Total  dissolved  gas  =2.299  vols. 


100.0 


The  composition  of  the  gases  in  water  saturated  with  chimney 
gases  may  be  calculated  in  the  same  manner. 


Composition  of 
gas,  per  cent. 

Volumes  of  gases  in  100  vols. 
water   • 

Percentage  com- 
position of  gas 
dissolved  by  water 

CO2      .                   10 

10  Xl  07   =10  70 

85.0 

O2                         10 

10X0  036=  0  36 

2.9    " 

N2  80 

80X0.019=   1.52 

12.1 

12.58 

100.0 

The  change  in  the  carbon  dioxide  from  10  per  cent,  of  the  gas 
sampled  to  85  per  cent,  of  the  gases  dissolved  in  water  shows  how 
serious  are  the  errors  which  can  arise  in  sampling.  If  the  sam- 
pling tank  originally  filled  with  pure  water  should  be  only  half 
emptied  so  that  it  would  be  half  filled  with  gas  of  the  above 
composition  and  half  filled  with  water,  and  then  it  should  be 
allowed  to  stand  till  equilibrium  were  attained,  7  per  cent,  of  the 
gas  would  be  dissolved  by  the  water  with  the  following  result. 


Original  composition 
of  gas,  per  cent. 

Composition  gas  after 
standing  over  water, 
per  cent. 

Composition  of 
gases  dissolved  by 
water,  per  cent. 

CO2  10.0 

5.2 

73.4 

O2                           10  0 

10  4 

5.0 

N2  80.0 

84.4 

21.6 

The  above  illustration  shows  that  in  chimney  gases  it  is  not 
at  all  impossible  to  have  an  error  of  50  per  cent,  in  the  CC>2 
through  carelessness  in  sampling.  Errors  of  similar  nature,  al- 
though hardly  of  such  large  proportions,  will  arise  with  other  gases. 
With  illuminating  gas  it  is  the  important  class  of  illuminants  of 


8  GAS  AND  FUEL  ANALYSIS 

the  ethylene  series  which  is  most  seriously  affected.  If  it  is 
worth  while  taking  a  sample  at  all  it  is  worth  while  to  saturate 
the  water  with  which  the  gas  is  to  come  in  contact. 

7.  Saturating  Water  in  Sampling  Tanks. — When  the  gas  to  be 
sampled  is  under  pressure  it  may  be  bubbled  through  the  water 
contained  in  a  bottle,  best  only  about  two-thirds  full  of  water 
and  loosely  stoppered.     The  air  of  the  bottle  will  soon  be  replaced 
by  the  gas  which  will  thus  act  on  the  constantly  changing  surface 
of  the  liquid  as  well  as  on  the  surface  exposed  to  the  bubbles. 
An  occasional  vigorous  shake  will  greatly  accelerate  absorption. 
Under  these  conditions  the  water  will  become  practically  saturated 
in  fifteen  minutes.     It  is  not  wise  to  attempt  to  saturate  water 
by  bubbling  the  gas  through  it  while  in  an  open  beaker,  since  the 
constant  presence  of  the  air  above  the  liquid  defeats  the  very 
object  aimed  at. 

The  water  in  tanks  of  the  form  shown  in  Fig.  2  may  be  readily 
saturated  if  suction  is  available  by  connecting  tank  1  to  the  gas 
main  as  shown  and  connecting  the  suction  pipe  to  cock  E.  The 
gases  will  then  bubble  through  the  water  and  pass  out  E.  Where 
suction  is  not  available  the  procedure  is  as  follows.  Start  with 
tank  1  full  of  water  and  tank  2  empty.  Fill  tank  1  with  gas  and 
connect  the  cocks  E  on  the  two  tanks  with  rubber  tubing.  Raise 
tank  2.  Water  will  flow  from  2  into  1  and  gas  from  1  to  2. 
When  each  is  approximately  half-full  close  the  valves  and  shake. 
Finish  passing  the  water  from  2  into  1  and  disconnect  the  rubber 
tube  from  E  of  tank  2.  Draw  a  fresh  tankful  of  gas  into  1, 
allowing  that  in  2  to  escape  into  the  air.  Connect  the  cocks  E 
with  rubber  tubes  as  before  and  repeat  the  process  of  dividing 
the  gas  and  water  between  the  two  tanks  and  shaking.  After 
three  such  operations  the  water  will  be  sufficiently  saturated. 

8.  Collecting  an  Average  Sample  Representative  of  a  Definite 
Period. — It  is  frequently  desirable  to   determine  the  average 
composition  of  gases  flowing  through  a  flue  for  a  period  of  time 
which  may  be  15  minutes  or  24  hours.     If  the  period  is  not 
longer  than  an  hour  the  use  of  two  cu.  ft.  tanks  as  shown  in  Fig.  2 
is  satisfactory.     A  represents  the  multiple  sampling  tube  pro- 
jecting into  a  flue.     B  is  a  calcium  chloride  tube  loosely  packed 
with  cotton  or  asbestos  to  filter  out  dust.     C  is  a  bubbling  tube 
to  indicate  the  rate  of  flow  of  the  gas.     The  first  step  in  a  test  is 


SAMPLING  AND  STORAGE  OF  GASES 


9 


to  saturate  the  water  of  the  tanks  as  previously  directed.  At 
the  close  of  this  operation  tank  1  should  be  full  of  water  and  tank 
2  of  gas  and  the  sampling  tube  and  the  filter  should  be  full  of  gas. 
To  commence  the  sampling  operation  D  is  opened  fully  and  F  is 
opened  slightly  until  gas  bubbles  through  C  at  the  rate  desired. 
It  is  a  mistake  to  open  widely  the  lower  stopcock  on  the  sampling 
tank  and  control  the  flow  of  gas  by  partially  closing  the  upper 
stopcock,  since  with  this  procedure  the  gas  in  the  tank  is  under 


FIG.  2. — Apparatus  for  aspirating  a  sample  of  gas  from  a  flue. 

an  unnecessarily  reduced  pressure  and  there  is  an  unnecessary 
risk  of  leakage.  The  gas  in  tank  2  escapes  through  the  open 
cock  at  the  top.  The  pressure  gage  at  G  will  indicate  if  the 
sampling  tube  or  the  filter  becomes  choked.  The  rate  of  gas  flow 
should  be  so  adjusted  that  tank  1  will  be  almost  filled  with  gas 
at  the  end  of  the  period.  There  should  still  remain  enough 
water  to  act  as  a  stirrer  for  the  gas  when  the  tank  is  shaken 
vigorously  to  mix  the  contents.  This  mixing  is  a  simple  precau- 
tion which  should  never  be  omitted.  It  is  true  that  gases  do 


10 


GAS  AND  FUEL  ANALYSIS 


mix  by  diffusion  but  the  rate  is  a  slow  one  and  it  is  never  safe  to 
rely  on  diffusion  to  give  a  fair  sample.  After  the  gas  in  tank  1 
is  mixed  a  portion  may  be  transferred  through  cock  E  to  a  labora- 
tory gas  holder  for  analysis.  To  get  ready  for  the  next  sample 
the  E  cocks  on  both  tanks  should  again  be  connected  by  the 
rubber  tube  and  the  gas  transferred  to  tank  2  so  that  the  water 
in  tank  2  will  remain  saturated. 

If  the  sampling  period  is  to  extend  for  much  more  than  an 
hour  the  flow  of  gas  through  the  sampling  tube  becomes  so  slow 
that  a  multiple  sampling  tube  is  not  to  be  relied  on.  The  use 
of  the  additional  apparatus  shown  in  Fig.  3  remedies  the  difficulty 
where  a  continuous  aspirator  is  available  to  draw  a  rapid  stream 
of  gas  through  the  sampling  tube.  The  gas  filter,  bubbling 
tube  and  sampling  tanks  of  Fig.  2  are  to  be  attached  to  cock  A 
of  Fig.  3.  The  sampling  tanks  may  then  be  set  to  take  as  slowly 


To  Aspirator 


FIG.  3. — Continuous  gas  sampling  apparatus. 

as  may  be  desired  a  portion  of  the  representative  rapidly  flowing 
gas  stream. 

In  Fig.  3,  B  is  a  pressure  gage  to  indicate  any  obstruction  of 
the  sampling  tubes,  C  is  a  bubbling  bottle  to  give  a  visual  control 
of  the  rate  of  the  stream,  D  is  a  gas  meter  which  may  be  omitted 
if  not  needed,  E  is  a  pressure  control  and  F  a  pressure  gage  on 
the  line  from  the  aspirator.  The  suction  on  the  sampling  tube 
as  shown  by  gage  B  should  be  only  a  few  tenths  of  an  inch  of 
water.  It  is  difficult,  however,  to  get  an  aspirator  to  work  prop- 
erly when  nearly  shut  off  so  that  the  aspirator  is  opened  enough 
to  work  efficiently  and  the  suction  on  the  line  is  kept  down  by  the 
regulator  E.  The  suction  on  B  may  be  regulated  by  the  depth 
to  which  the  tube  in  E  is  immersed. 

The  title  of  this  section  calls  for  the  collection  of  a  sample 
representative  of  a  definite  period.  The  foregoing  procedure 


SAMPLING  AND  STORAGE  OF  GASES  11 

only  accomplishes  it  approximately.  In  order  that  the  sample 
should  be  truly  representative  a  given  proportion,  say  one-tenth 
of  1  per  cent,  of  the  gas,  should  be  constantly  passing  through  the 
sampling  tube.  If  the  flow  of  gas  in  the  main  dropped  to  one- 
third  of  its  former  rate,  the  flow  of  gas  through  the  sampling 
tube  and  into  the  sampling  tank  should  also  decrease.  The 
ideal  to  be  striven  for  is  to  have  in  the  small  sampling  tank  gas 
of  the  identical  composition  that  there  would  be  in  a  large  gas  holder 
where  all  of  the  main  gas  stream  had  been  gathered  and  mixed. 
This  can  only  be  accomplished  by  a  sampler  which  takes  repre- 
sentative quantities  as  well  as  qualities  of  gas.  The  sampling 
apparatus  described  is  supposed  to  work  at  a  constant  and  not  a 
proportionate  rate,  but  it  does  not  even  do  this  accurately. 
It  is  not,  however,  possible  to  take  a  truly  proportional  sample 
without  great  elaboration  of  equipment  and  the  method  described 
is  usually  sufficient. 

9.  Collecting  a  Representative  Instantaneous  Sample. — The 
problem  of  a  representative  instantaneous  sample  is  in  some  ways 
simpler  than  that  involved  in  collecting  a  sample  to  represent  a 
longer  period.     If  the  apparatus  shown  in  Fig.  3  is  attached  to  a 
multiple  sampling  tube  a  sample  drawn  at  A  should  be  fairly 
representative.     If  desired  an  Orsat  burette  or  similar  apparatus 
may  be  attached  permanently  at  A. 

10.  Storing  Gas  Samples. — Samples  of  gas  obtained  as  directed 
in  the  preceding  section  are  too  large  for  ready  transportation 
to  the  laboratory  for  analysis.     It  is  usually  convenient  to  trans- 
fer a  portion  to  a  small  glass  gas  holder  which  is  advantageously 
of  the  type  proposed  many  years  ago  by  Hempel  and  shown  in 
Fig.  4.     This  consists  of  a  bulb  terminated  above  by  the  gas 
inlet  of  capillary  tubing  bent  in  the  form  of  a  U  to  allow  a  water 
seal  and  at  the  bottom  by  a  larger  tube  for  the  water  supply. 
The  transfer  of  gas  is  accomplished  in  the  following  stages. 
Attach  at  cock  E  of  Figs.  2  and  4  a  glass  tee  carrying  at  A  a 
rubber  connection  and  a  small  funnel  and  at  B  a  rubber  con- 
nection.    Fill  the  gas  holder  with  water  taken  from  the  large 
sampling  tank  2  of  Fig.  2,  which  is  saturated  with  the  gas,  and 
connect  the  gas  holder  at  B  as  shown  in  Fig.  4,  with  the  exception 
of  the  screw  clamps  at  A  and  B.     Open  valve  E  and  blow  gas 
through  the  tee  and  out  A  to  expel  air.     Close  E  and  force  water 


12 


GAS  AND  FUEL  ANALYSIS 


from  the  small  gas  holder  into  the  funnel.  Tighten  clamp  A. 
Fill  the  glass  gas  holder  nearly  full  of  gas  and  close  E.  Open  A 
cautiously  and  allow  water  to  flow  from  the  funnel  and  fill  the 
capillary  seal  of  the  gas  holder.  Close  clamp  B  and  disconnect 
the  gas  holder  from  the  tee.  Elevate  the  levelling  bottle  so  as 
to  put  the  gas  in  the  holder  under  slight  pressure,  and  close  the 
clamp  C  at  the  bottom  of  the  holder.  The  gas  is  now  stored  in  a 


FIG.  4. — Glass  gas  holder  for  storing  samples. 

glass  vessel  closed  at  the  top  by  a  capillary  tube  filled  with  water, 
which  in  turn  is  closed  by  a  clamped  rubber  tube  at  the  top  of 
the  capillary.  At  the  bottom  the  holder  is  similarly  closed  by  a 
column  of  water.  The  gas  is  thus  in  contact  with  nothing  but 
glass  and  water  and  if  the  latter  has  been  previously  saturated, 
may  be  preserved  without  change  for  months.  The  above  form 
of  gas  holder  is  always  reliable. 


SAMPLING  AND  STORAGE  OF  GASES  13 

Gas  holders  of  the  floating  type  are  not  to  be  relied  upon  for 
there  is  always  diffusion  of  gases  through  the  water,  and  after 
several  hours  evident  changes  may  be  found.  There  are  nu- 
merous forms  of  gas  holders  where  stopcocks  are  relied  upon  to 
prevent  leakage.  Stopcocks  may  be  tight  or  they  may  not  and 
anyone  who  has  had  experience  with  the  irritating  doubts  attend- 
ant upon  their  use  will  prefer  not  to  trust  them  more  than  is 
necessary.  The  same  thing  holds  true  of  rubber  stoppers  and 
connections.  Gases  may,  however,  be  transported  quite  safely 
in  glass  bottles  with  rubber  stoppers  provided  a  little  water  is 
left  in  the  bottle  and  the  stopper  is  wired  tightly  in  and  covered 
thickly  with  paraffine.  The  bottle  is  then  to  be  kept  upside  down. 
Under  these  conditions  the  small  amount  of  water  in  the  bottle 
forms  a  seal  on  the  inside  and  the  paraffine  a  seal  on  the  outside, 
re-enforcing  the  rubber.  When  samples  of  this  sort  are  to  be 
shipped  by  express  they  should  be  packed  in  crates  without  a  top 
so  that  care  will  always  be  taken  to  keep  the  proper  end  up. 
Where  gases  have  to  be  stored  a  long  time  and  especially  where 
they  must  be  shipped,  the  truly  safe  way  is  to  collect  them  in 
glass  tubes  drawn  out  at  each  end  and  fuse  the  ends  in  a  blowpipe 
flame. 


CHAPTER  II 
GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS 

1.  Introduction. — Gas  analysis  is  an  extremely  useful  method 
for  controlling  the  operation  and  checking  the  efficiency  of  many 
industrial  operations.  All  of  the  manifold  industries  using  fuel 
as  a  source  of  heat  and  almost  all  industries  engaged  in  producing 
fuel  or  utilizing  it  in  any  way  find  in  gas  analysis  a  valuable 
assistant.  There  are  very  many  special  industries  which  require 
the  analysis  of  gases  which  are  peculiar  to  themselves  and  not 
connected  with  fuels,  but  though  the  general  methods  of  gas 
analysis  here  given  will  often  apply  to  these  cases,  no  attempt 
will  be  made  to  develop  those  applications  which  might  better 
be  taken  up  in  connection  with  a  study  of  the  particular  indus- 
tries. This  chapter  will  consider  only  the  gases  arising  from  the 
utilization  of  fuels. 

The  purpose  for  which  the  analysis  is  desired  will  influence 
the  methods  to  be  employed  and  the  kind  of  apparatus  to  be 
used,  for  time  consumed  and  liability  to  errors  increase  rapidly 
with  the  number  of  constituents  to  be  determined.  The  analysis 
is  to  be  made  as  simply  as  pos'sible,  small  percentages  of  gases 
unimportant  for  the  purpose  of  the  analysis  being  neglected  and 
groups  of  related  gases  being  frequently  determined  together. 
In  boiler  firing  and  in  the  operation  of  all  furnaces  heated  by 
combustion  of  fuel,  the  variations  in  the  percentages  of  carbon 
dioxide,  oxygen  and  carbon  monoxide  show  at  once  the  changes 
in  efficiency  of  the  furnace.  In  the  operation  of  gas  producers 
these  three  constituents  with  the  added  determination  of  hydro- 
carbons and  of  hydrogen  suffice  for  most  purposes.  When  gas 
is  to  be  sold  to  consumers,  as  is  the  case  with  a  city  gas  supply, 
a  more  complete  analysis  is  often  necessary  and  not  infrequently 
some  uncommon  and  minute  constituents  must  be  sought  as  an 
explanation  of  trouble. 

This  adaptation  of  the  means  to  the  end  is  a  characteristic  of 
technical  analysis,  which  seeks  only  the  particular  information 

14 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      15 

of  value  for  the  purpose  in  hand.  On  this  account  gases  from 
different  sources  will  be  considered  separately,  although  there 
may  be  much  in  common  between  them.  There  are  various 
operations  common  to  almost  all  processes  of  gas  analysis  which 
may  well  be  considered  before  passing,  to  special  cases,  and 
such  general  considerations  form  the  subject  of  this  chapter. 

2.  General  Method. — The  method  preferably  followed  in 
technical  gas  analysis  requires  a  measurement  of  the  initial 
volume  of  the  mixed  gas,  the  absorption  of  a  single  constituent 
by  an  appropriate  reagent,  and  the  measurement  of  the  new 
volume,  the  constituent  absorbed  being  determined  by  difference. 
Where  no  suitable  absorbent  is  known  for  a  given  constituent 
it  is  desirable  to  transform  the  gas  into  some  more  suitable 
compound.  It  is  necessary  in  order  that  these  changes  in  volume 
due  to  absorption  be  correctly  noted,  that  the  temperature  and 
pressure  of  the  gas  be  known  at  each  step,  and  it  would  be  ideal 
if  both  the  temperatures  and  pressures  could  be  kept  absolutely 
constant  throughout  the  process.  This  can  never  be  accom- 
plished, although  by  special  apparatus  described  in  Chapter  VI 
on  Exact  Gas  Analysis  errors  due  to  change  in  external  tem- 
perature and  pressure  during  an  analysis  may  be  automatically 
eliminated.  This  procedure  is,  however,  more  complicated 
than  is  necessary  for  technical  work  where  it  is  usually  suf- 
ficiently accurate  to  make  the  assumption  that  the  temperature 
of  a  water-jacketed  burette  in  a  laboratory  does  not  vary  during 
the  hour  that  may  be  required  for  an  analysis,  and  that  the 
barometric  pressure  does  not  change  in  the  same  period.  Since 
this  simpler  procedure  is  sufficiently  accurate  for  most  technical 
purposes,  it  will  be  described  first.  The  historical  development 
of  the  present  apparatus  and  methods  is  discussed  in  Chapter  VI 
on  Exact  Gas  Analysis. 

3.  The  Gas  Burette. — The  gas  burette  has  its  zero  point 
at  the  top  and  is  usually  of  100  c.c.  capacity.  It  is  closed  at  the 
•top  by  a  stopcock  or  sometimes  simply  by  a  rubber  tube  and  a 
pinchcock  and  should  always  be  enclosed  in  a  water  jacket. 
Almost  all  forms  of  gas  burettes  will  answer  the  above  descrip- 
tion, but  there  are  many  differences  of  detail,  the  most  impor- 
tant being  the  style  of  the  stopcock  which  closes  the  burette  at 
the  top.  The  form  of  apparatus  which  has  been  evolved  in 


16 


GAS  AND  FUEL  ANALYSIS 


the  laboratory  of  the  University  of  Michigan1  and  which  has 
given  good  service  during  the  past  ten  years  is  shown  in  Fig.  5, 
which  illustrates  the  apparatus  as  it  appears  in  service. 
Details  are  given  in  Fig.  6.  The  burette-stand  may  "be  im- 
provised from  an  ordinary  iron  stand,  one  of  whose  rings  of  ex- 
ternal diameter  slightly  greater  than  the  water  jacket  of  the 
burette  has  been  provided  with  a  brass  collar,  thus  making  a 


B  C 


A. 


RubberStoppgr 


FIG.  5. — Gas  burette  and 
pipette. 


100  c.c.  divided 


^  RubberStopper 


FIG.  6.— Details  of  gas  burette. 


cup  in  which  the  rubber  stopper  of  the  water  jacket  rests  without 
binding.  Another  ring  large  enough  to  slip  loosely  over  the 
water  jacket  serves  to  keep  the  burette  vertical.  A  segment 
is  sawed  out  of  the  front  of  this  ring  to  allow  an  uninterrupted 
view  of  the  graduations,  and  it  is  wrapped  with  chamois  skin 
until  it  fits  as  snugly  as  desired.  A  spring  clamp  made  from 
sheet  brass  makes  a  more  elegant  upper  support.  By  this  simple 
arrangement  the  burette  may  be  raised,  lowered,  or  swung  to 

1  White  and  Campbell,  J.  Am.  Chem.  Soc.,  27,  734  (1905). 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      17 

one  side  at  the  convenience  of  the  operator,  and  may  be  tipped 
in  any  position  while  carrying,  without  danger  of  breakage. 

By  reference  to  A  of  Fig.  6  it  will  be  seen  that  the  body  of 
the  burette  is  a  perfectly  straight  tube.  It  is  closed  at  the  bottom 
by  a  one-hole  rubber  stopper,  which  need  not  even  be  wired  in, 
unless  the  burette  is  to  be  filled  with  mercury.  To  clean  the 
burette,  all  that  is  necessary  is  to  take  out  the  rubber  stopper 
and  lift  the  burette  and  its  jacket  out  of  the  rings  when  it  may 
be  turned  upside  down,  swabbed  out  as  an  ordinary  burette, 
and  then  swabbed  with  a  clean  dry  muslin  which  is  more  efficient 
than  a  wet  cloth  in  removing  the  film  of  grease  which  causes 
the  drops  to  hang  to  the  glass.  Caustic  soda  may  be  used  or 
chromic  acid,  but  they  are  not  usually  necessary. 

4.  Care  of  Stopcock. — The  stopcock  of  a  gas  burette  is  very 
carefully  ground  and  polished  so  as  to  be  as  nearly  gas  tight  as 
possible.  Particles  of  grit  getting  into  the  capillary  opening 
are  apt  to  cut  a  groove  around  the  stopcock  so  the  opening  is 
bored  diagonally  in  order  that  the  grooves  worn  in  this  manner 
may  be  parallel  and  non-connecting.  This  device  is  of  assistance 
but  the  stopcock  must  still  be  handled  carefully. 

To  keep  in  good  condition  remove  the  stopcock  from  the 
burette,  wipe  it  off  with  a  dry 'cloth  and  see  that  the  capillary 
openings  are  clean.  Do  the  same  with  the  seat  into  which  it 
fits  in  the  burette  and  the  capillaries  with  which  it  connects. 
Rub  a  thin  coat  of  some  lubricant  over  the  stopcock.  Vaseline 
is  inferior.  A  material  made  by  melting  one  part  of  best  black 
rubber  at  as  low  a  temperature  as  possible  and  stirring  into  it 
one  part  of  paraffine  and  one  part  of  vaseline  answers  well  when 
it  is  carefully  made.  The  author  has  found  anhydrous  lanolin 
the  best  material.  The  lubricated  stopcock  should  be  pressed 
gently  into  the  dried  seat  and  turned  a  couple  of  times,  when 
the  space  between  the  stopcock  and  the  seat  should  appear 
perfectly  translucent  without  air  bubbles  or  any  discontinuity. 
If  too  much  lubricant  is  used  it  will  work  itself  into  the  capillaries 
and  clog  them.  If  either  the  stopcock  or  the  seat  is  wet  the 
lubricant  will  not  adhere  well.  These  stopcocks  are  expensive 
and  it  is  advisable  to  fasten  them  to  the  burette  with  a  fine 
copper  wire  attached  to  the  stopcock  so  loosely  that  it  can 
turn  readily.  It  is  not  advisable  to  use  a  rubber  band  for  this 


18  GAS  AND  FUEL  ANALYSIS 

purpose  since  it  sticks  to  the  handle  of  the  stopcock  and  exerts 
a  torsion  sufficient  sometimes  to  turn  the  cock  at  an  inopportune 
time.  The  stopcock  should  always  be  loosened  in  its  seat  when 
the  burette  is  to  be  put  away  and  it  is  admirable  policy  to 
always  clean  it  and  make  it  ready  for  use  again  before  setting  it 
aside. 

5.  Saturating  the  Water  of  the  Burette.— The  liquid  filling 
the  burette  is  almost  always  water  which  allows  much  more 
rapid  and  convenient  and  in  some  ways  more  accurate  manipula- 
tion  than   mercury    does.     It   should   be   saturated   with    gas 
similar  to  that  which  is  to  be  analyzed.     If  the  gas  is  air  this 
precaution  may  often  be  omitted,  since  distilled  water  is  usually 
saturated  with  air.     The  precaution  should  not  be  omitted  with 
other  gases,  especially  those  like  flue  gases  rich  in  the  more 
soluble  carbon  dioxide.     The  errors  due  to  solubility  of  gases 
are  discussed  more  fully  in  Section  6  of  Chapter  I.     Place  200 
c.c.  of  water  in  a  flask  or  bottle  of  about  400  c.c.  capacity  and 
lead  in  a  stream  of  gas  through  a  glass  tube  passing  through  a 
loosely  fitting  cork,  shaking  occasionally.     If  the  supply  of  gas 
is  limited  a  smaller  flask  may  be  used  and  the  loose  cork  may 
be  pressed  down  tight  after  the  air  has  been  displaced.     Shaking 
the  flask  facilitates  absorption.'    It  is  not  necessary  that  the 
water  be  absolutely  saturated  and  five  minutes  is  usually  ample 
time  for  the  operation. 

6.  Drawing  the  Sample  of  Gas  into  the  Burette. — The  gas 
to  be  analyzed  is  assumed  to  be  contained  in  a  gas  holder  of  a 
type  similar  to  that  shown  in  Fig.  4  of   Chapter   I,  but   the 
directions  for  use  of  this  type  of  gas  holder  may  readily  be 
adapted  to  other  types. 

The  tubing  to  connect  the  burette  and  gas  holder  should  be 
capillary  so  that  the  air  contained  in  it  may  be  completely 
swept  out  without  wasting  much  gas.  A  tube  of  1  mm.  internal 
diameter  answers  well.  It  should  not  be  rubber  because  rubber 
absorbs  heavy  hydrocarbons  from  gases  rich  in  these  bodies 
and  gives  them  back  again  to  gases  containing  them  in  but 
small  amount.  It  is  necessary  to  make  one  rubber  connection 
at  each  end  of  the  capillary  tube  but  the  surface  of  rubber 
exposed  to  the  action  of  the  gases  should  be  reduced  to  a  minimum 
by  bringing  the  ends  of  the  glass  capillary  tubes  into  direct 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      19 

contact  with  each  other,  or,  if  it  is  necessary  to  leave  a  pinch- 
cock  on  the  rubber,  as  close  to  each  other  as  possible.  The 
glass  tubes  should  be  cut  off  square  and  the  sharp  edges  softened 
in  a  flame  sufficiently  to  prevent  the  cutting  of  the  rubber  but 
not  enough  to  constrict  the  capillary  opening  of  the  glass  tube. 
The  rubber  tube  should  fit  tightly  to  the  glass  and  be  of  the 
best  quality  black  gum  rubber,  free  from  any  internal  ridge 
where  the  seam  has  been  joined.  The  inside  of  the  rubber  tube 
may  be  moistened  with  water  or  preferably  with  glycerine  to 
make  it  slip  more  readily  over  the  glass.  The  rubber  connec- 
tions to  the  capillary  should  be  bound  with  wire  as  a  further 
safeguard  against  leakage.  Soft  copper  wire  of  about  22  B.  & 
S.  gage  is  suitable.  Finer  wire  is  too  apt  to  cut  the  rubber. 
Heavier  wire  is  apt  not  to  pull  up  snugly.  Copper  wire  of  24 
B.  &  S.  gage  insulated  with  cotton  and  paraffined  like  that 
used  for  annunciators,  is  the  best  material  as  it  is  strong  enough 
and  does  not  cut  the  rubber.  It  is  a  mistake  to  wrap  the  wire 
several  times  around  the  tube.  A  piece  of  wire  about  2  in. 
long  should  be  wrapped  once  around  the  tube.  The  crossed 
ends  are  then  to  be  grasped  close  to  the  rubber  with  a  pair  of 
pliers  and  tightened  with  a  single  half  turn  of  the  wrist. 

No  rubber  joint  can  be  relied  on  to  be  gas-tight  for  a  long 
period  of  time.  A  joint  prepared  as  directed  here  should,  how- 
ever, not  allow  any  perceptible  leakage  in  the  course  of  a  gas 
analysis  although  it  is  wiser  not  to  subject  it  to  any  higher  gas 
pressure  or  suction  than  necessary. 

The  method  of  connecting  the  gas  holder  and  the  burette 
is  shown  in  Fig.  7  where  A  is  the  gas  holder,  D,  a  bent  capillary 
tee  tube  and  F  the  gas  burette.  Before  making  the  connections 
the  gas  burette  is  to  be  filled  with  saturated  water  and  the  cock 
closed  by  a  turn  of  180°  which  completely  seals  both  the  capil- 
laries below  and  above  the  cock.  The  capillary  tee  tube  is  to 
be  inserted  into  the  open  rubber  tube  above  the  clamp  B,  con- 
nected at  E  as  shown  and  the  joints  are  to  be  wired.  The  gas 
in  the  holder  is  to  be  put  under  pressure  by  raising  the  levelling 
bottle  and  clamp  B  opened.  Cock  C  is  then  opened  slightly 
until  the  water  in  the  capillary  of  the  gas  holder  rises  to  displace 
all  the  air  in  the  funnel  arm.  Cock  C  is  then  closed  and  cock  F 
turned  90  degrees  to  the  position  shown  in  Fig.  7  and  at  B  in 


20 


GAS  AND  FUEL  ANALYSIS 


Fig.  6.  The  rest  of  the  water  in  the  capillary  A  moves  through 
D  and  out  F  driving  all  air  ahead  of  it.  Some  gas  may  also 
blow  out  if  the  manipulator  is  not  skilful,  but  this  does  no 
harm.  Cock  F  is  then  turned  90  degrees  opening  the  passage 
to  the  burette  as  shown  at  A  in  Fig.  6  and  the  gas  passes  into 
the  burette.  When  enough  gas  is  in  the  burette  another  90- 


FIG.  7. — Gas  burette  and  gas  holder. 

degree  turn  of  the  cock  in  the  same  direction  to  the  position  C 
of  Fig.  6  stops  the  gas  flow.  A  few  cubic  centimeters  of  water 
are  placed  in  the  funnel  above  C  (Fig.  7),  the  pressure  in  the 
gas  holder  is  changed  to  suction,  cock  C  is  opened  and  water 
flows  into  the  capillary  of  the  gas  holder  re-establishing  the 
seal.  The  clamp  B  may  then  be  closed  and  the  capillary 
disconnected.  This  procedure  allows  transfer  of  the  gas  without 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      21 

possibility  of  change  in  composition  and  restores  the  seal  of 
the  gas  holder  at  the  close  of  the  operation.  Instead  of  the 
tee  with  cock  and  funnel  blown  as  one  piece  the  simpler  apparatus 
shown  in  Fig.  4  of  Chapter  I  may  be  used. 

7.  Measuring  a  Gas  Volume. — The  volume  of  gas  is  to  be 
measured  at  the  temperature  of  the  water  jacket  and  at  baro- 
metric pressure.  The  temperature  of  the  gas  as  drawn  into 
the  burette  does  not  ordinarily  differ  very  many  degrees  from 
that  of  the  jacket  water  but  it  should  be  allowed  to  stand  a 
few  moments  to  allow  it  to  attain  that  temperature.  During 
these  minutes  the  gas  if  not  already  saturated  with  moisture 
rapidly  absorbs  it  from  the  moist  burette  walls  and  becomes 
saturated  as  it  should  be  before  its  volume  is  measured. 

Delay  in  reading  the  volume  is  also  necessary  to  allow  the 
film  of  water  which  adheres  to  the  burette  walls  as  the  sample 
is  rapidly  drawn  in,  to  run  down.  If  the  walls  of  the  burette 
are  clean  the  water  will  have  run  down  in  three  minutes  so 
completely  that  the  volume  has  become  approximately  constant. 
If  this  precaution  is  neglected  the  volume  read  may  easily  be 
in  error  by  0.2  c.c.,  even  with  a  clean  burette.  Some  operators 
object  to  this  three-minutes  wait  as  too  great  hindrance  to  rapid 
work  and  it  is  true  that  if  the  readings  are  made  by  a  skillful 
operator  immediately  after  the  introduction  of  the  gas,  the 
errors  of  successive  readings  are  almost  constant  and  disappear 
in  the  subtractions.  If,  however,  the  practice  is  followed  of 
detaching  the  used  pipette  and  connecting  the  new  one  before 
reading  the  volume  of  gas,  sufficient  time  will  have  elapsed 
without  the  operator's  having  been  idle. 

To  obtain  a  sample  of  exactly  100  c.c.  a  sample  of  slightly 
more  than  100  c.c.  is  initially  taken  and  compressed  by  raising 
the  levelling  bottle  until  the  bottom  of  the  meniscus  is  exactly 
opposite  the  100  c.c.  mark.  The  stopcock  at  the  bottom  of 
the  burette  is  then  closed  so  that  the  mensicus  cannot  change  its 
position  and  the  stopcock  at  the  top  of  the  burette  opened  momen- 
tarily to  the  air,  to  allow  the  pressure  in  the  burette  to  equalize 
itself  with  the  outside  air.  The  volume  of  gas  should  now  be 
100  c.c.  at  atmospheric  pressure  but  the  correctness  of  the 
volume  should  be  checked  by  opening  the  stopcock  connecting 
the  levelling  bottle  with  the  burette  and  raising  the  levelling 


22  GAS  AND  FUEL  ANALYSIS 

bottle  until  its  water  surface  is  at  the  same  height  as  that  of  the 
water  in  the  burette.  The  connecting  stopcock  may  now  be 
closed  and  the  volume  read  as  indicated  by  the  bottom  of  the 
meniscus.  If  the  operation  has  been  properly  carried  out  the 
volume  should  be  exactly  100  c.c.  This  volume  is  subject  to 
correction  for  error  in  the  burette  and  if  an  exact  100  c.c.  sample 
is  desired  the  meniscus  may  have  to  be  set  on  some  other  figure 
than  the  100  mark. 

8.  Calibration  of  a  Gas  Burette. — A  gas  burette  may  be 
calibrated  like  any  other  form  of  burette  by  wiring  a  one-hole 
rubber  stopper  carrying  a  stopcock  into  the  bottom  of  the 
burette  and  weighing  the  water  delivered.  Burettes  of  good 
quality  are  usually  calibrated  accurately  enough  throughout 
their  cylindrical  portion  to  make  this  form  of  calibration  unneces- 
sary for  technical  work.  The  burette  should,  however,  be  cali- 
brated in  its  upper  portion,  especially  if  its  previous  history 
is  not  definitely  known,  since  its  original  stopcock  may  have 
been  broken  and  the  volume  of  the  neck  changed  when  a  new 
stopcock  was  fused  on,  and  since  it  may  have  been  calibrated 
by  the  maker  to  be  used  when  filled  with  mercury  instead  of 
with  water.  The  error  in  this  latter  case  arises  from  the  custom 
of  reading  the  mercury  meniscus  at  the  top  of  its  convex  surface 
and  the  water  meniscus  at  the  bottom  of  its  concave  surface. 
It  will  be  readily  seen  that  if  the  mercury  meniscus  stands  at 
10  c.c.  there  will  be  more  gas  in  the  burette  than  if  the  same 
burette  is  filled  with  water  with  the  bottom  of  its  meniscus  at 
10  c.c.  This  error  may  amount  to  0.2  c.c.  in  an  ordinary  burette. 
Both  of  these  errors  are  constant  ones  throughout  the  cylindrical 
portion  of  the  burette  and  independent  of  the  volume  of  gas  in  the 
burette.  It  will  therefore  be  sufficient  to  determine  them  once. 

The  most  convenient  method  is  to  compare  one  burette  with 
another.  Draw  into  each  burette  about  10  c.c.  of  air,  the 
exact  amount  being  entirely  immaterial.  It  is  only  necessary 
that  the  volume  be  large  enough  so  that  the  reading  is  in  the 
cylindrical  portion  of  the  burette.  It  is  not  desirable  that  the 
volume  be  large  since  the  error  caused  by  water  adhering  to 
the  walls  of  the  burette  increases  with  the  size  of  the  sample. 
Connect  the  burettes  by  a  bent  capillary  tube  making  the 
rubber  connections  while  the  stopcock  of  one  of  the  burettes  is 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      23 

open  to  the  air  so  that  the  air  enclosed  in  the  capillary  will  be 
under  atmospheric  pressure.  Read  the  volume  of  the  air  in 
each  burette  at  atmospheric  pressure  as  usual.  We  will  assume 
that  Burette  A  which  has  an  unknown  constant  error  "x"  is 
the  one  being  tested  and  that  Burette  B  is  the  one  assumed  to 
be  correct  throughout  its  cylindrical  portion,  although  it  may 
itself  have  a  similar  unknown  constant  error  "  y. "  Transfer 
all  of  the  air  from  A  to  B  stopping  the  water  in  A  just  at  the 
stopcock  and  read  the  new  volume  in  B.  The  notes  will  then 
read  somewhat  as  follows: 

CALIBRATION  OF  BURETTE  A  AGAINT  BURETTE  B 

Burette  A  B 

Initial  vol.  air  10.6  c.c.+x          9.5  c.c.+y 
Second  reading       0  20.3  c.c.+y 


Subtracting      10.6  c.c.+x  =   10.8  c.c. 
x=+0.2.  c.c. 

This  result  translated  into  words  means  that  there  must  be 
added  to  each  reading  of  Burette  A  0.2  c.c.  Since  the  probable 
error  of  observation  is  0.1  c.c.  several  successive  determinations 
should  be  made  and  the  mean  taken. 

It  is  always  wiser  to  record  this  error  in  the  notebook  after 
each  reading,  92.5+0.2,  and  not  simply  make  the  correction 
mentally  and  record  92.7,  since  there  may  always  come  a  time 
when  the  analyst  will  be  in  doubt  as  to  whether  he  has  made 
the  mental  correction  or  forgotten  to  make  it  before  recording. 
This  error  automatically  disappears  whenever  one  Volume  is 
subtracted  from  another  and  it  is  therefore  only  necessary  to 
apply  it  when  the  absolute  volume  needs  to  be  known  as  is  the 
case  with  the  initial  volume  taken  for  analysis.  This  makes 
the  error  vastly  less  important  than  it  would  be  otherwise,  for 
if  in  an  analysis  of  flue  gas  an  apparent  100  c.c.  sample  is  taken 
which  becomes  when  corrected  100.2  c.c.,  and  10  c.c.  is  found 
to  be  C02,  the  percentage  of  C02,  neglecting  the  burette  calibra- 
tion, is  found  to  be  10.00  per  cent,  and  allowing  for  the  calibra- 
tion 9.98  per  cent.,  which  when  rounded  off  becomes  10.0  per 
cent,  as  before.  The  case  is  different,  however,  when  a  sample 
of  10.0  c.c.  is  taken  as  is  the  case  in  explosion  analysis.  If  the 


24 


GAS  AND  FUEL  ANALYSIS 


analysis  showed  8.0  c.c.  of  hydrogen,  the  percentage  neglecting 
the  calibration  would  be  figured  as  80.0  per  cent,  but  allowing 
for  the  calibration  would  be  78.4  per  cent.  It  is  preferable  to 
record  the  calibration  correction  even  though  it  may  be  later 
neglected  in  the  calculation. 

9.  Gas  Pipettes. — The  various  gases  are  determined  so  far 
as  possible  by  absorption  in  suitable  reagents  contained  in 
pipettes  of  the  form  shown  in  A,  B,  and  C  of  Fig.  8.  The  use  of  a 
separate  pipette  for  each  reagent  was  first  brought  into  general 
use  by  Hempel.  These  pipettes  differ  from  his  in  the  elimination 
of  the  deep  U  bend  in  the  capillary,  which  is  retained  only  in  the 
explosion  pipette.  This  deep  bend  is  a  distinct  disadvantage 


A. 


C. 


FIG.  8. — Details  of  gas  pipettes. 

since  drops  of  reagent  collect  in  it  and  are  later  carried  into  the 
burette.  It  is  no  longer  needed  when  used  with  the  burette 
just  described.  These  pipettes  are  mounted  on  wooden  stands, 
as  shown  in  Fig.  5,  which  should  be  paraffined  and  not  shel- 
lacked so  that  they  may  not  be  affected  by  reagents  accidentally 
spilled. 

10.  Connecting  the  Burette  and  Pipette. — The  greatest 
manipulative  error  with  most  forms  of  gas  analysis  apparatus 
comes  from  the  frequent  changes  of  pipettes  necessary.  Unless 
the  operator  is  skilful  there  is  danger  of  loss  of  gas  or  inclusion 
of  air.  The  form  of  burette  just  described  prevents  this  error. 
The  general  arrangement  of  the  burette  and  pipette  is  shown  in 
Fig.  5.  The  stopcock  A  is  turned  to  the  position  shown  at  B  in 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS     25 

Fig.  6,  the  bent  capillary  B  whose  dimensions  are  immaterial, 
is  connected  to  the  burette  and  pipette  and  the  rubber  joints 
are  wired.  The  operator  blows  through  the  rubber  tube  (D  of 
Fig.  5)  on  the  last  bulb  of  the  pipette,  forces  the  liquid  from  the 
pipette  up  the  capillary  and  over  to  the  stopcock,  driving  all 
the  air  ahead  of  it,  and  closes  the  stopcock  by  turning  it  90° 
to  the  position  D  of  Fig.  6.  The  capillary  tube  is  now  entirely 
full  of  liquid  and  the  operator  has  only  to  compress  the  gas  in 
the  burette  by  raising  the  levelling  bottle,  and  turn  the  stopcock  a 
half  turn  to  the  proper  position  (A  of  Fig.  6)  when  the  gas  will 
pass  into  the  pipette.  By  this  method  of  manipulation,  it  is 
easy  to  transfer  the  gas  from  burette  to  pipette  without  loss  or 
inclusion  of  air.  Furthermore,  since  the  volume  of  the  capillary 
is  entirely  immaterial,  it  may  be  chosen  of  larger  diameter  than 
usual,  permitting  more  rapid  work  and  lowering  the  pressure 
necessary  to  force  the  gas  through  it  rapidly.  It  has  been 
found  advantageous  to  have  the  stopcock  left-handed,  as  indi- 
cated, so  that  the  hand  manipulating  the  stopcock  may  not 
interfere  with  a  clear  view  of  the  meniscus  of  the  liquid  advancing 
along  the  capillary  tube. 

11.  Details  of  a  Simple  Gas  Analysis. — Accuracy  in  gas 
analysis  is  dependent  on  the  exercise  of  very  great  care  in  ma- 
nipulation. When  the  analysis  is  completed  there  is  no  way  of 
going  back  over  the  ground  again  as  may  so  frequently  be  done 
in  ordinary  chemical  analysis,  and  it  is  not  always  possible  to 
make  duplicate  analyses.  The  analyst  must  be  able  to  state 
with  confidence  that  every  precaution  was  taken  to  ensure  an 
accurate  result.  Detailed  directions  will  be  given  for  the 
analysis  of  a  gas  which  may  be  assumed  to  be  air.  This  is  a 
very  convenient  material  for  practice  since  it  may  be  obtained 
in  unlimited  quantities  and  of  practically  constant  composition. 

The  burette  is  to  be  cleaned  (§3),  the  stopcock  lubricated 
(§4),  and  the  water  saturated  (§5).  Draw  the  sample  of  gas 
into  the  gas  burette  (§6),  measure  it  (§  7),  and  connect  it  to  a 
pipette  containing  KOH  (§  10),  for  determination  of  C02. 
The  connections  having  been  properly  made  and  the  air  driven 
out  of  the  capillary  tube  as  indicated,  raise  the  levelling  bottle 
and  pass  the  gas  into  the  absorbent,  letting  the  water  of  the 
burette  follow  until  it  reaches  the  bottom  of  the  capillary  of 


26  GAS  AND  FUEL  ANALYSIS 

the  pipette.  The  gas  is  now  all  in  the  pipette.  Let  it  remain 
for  about  three  minutes  gently  shaking  the  pipette  occasionally 
to  agitate  the  gases  and  cause  more  rapid  absorption.  When 
it  is  believed  that  absorption  is  complete  pass  1  c.c.  of  the 
burette  water  into  the  pipette  to  rinse  from  the  capillary  any 
reagents  which  might  have  been  splashed  into  it,  and  then  draw 
back  the  gas  into  the  burette,  pulling  the  liquid  of  the  pipette 
as  far  as  the  stopcock  on  the  burette.  By  a  quarter  turn  of 
the  stopcock  to  position  B  of  Fig.  6  the  connection  between  the 
pipette  and  the  burette  is  closed  while  that  from  the  pipette  to 
the  air  is  open.  This  causes  the  reagent  to  siphon  back  into 
the  pipette.  After  waiting  for  three  minutes  to  allow  the 
liquid  to  drain  from  the  walls  of  the  burette  read  the  volume 
as  before  and  report  the  decrease  in  volume  as  the  volume  of  the 
C02  absorbed.  There  is  no  certainty  that  all  the  gas  has  been 
absorbed.  The  only  way  for  the  operator  to  be  sure  is  to  pass 
the  gas  back  again  into  the  pipette  and  repeat  the  operation 
until  the  volume  remains  constant.  Disconnect  the  pipette 
from  the  capillary  tube,  and  rinse  out  the  capillary  tube  with 
the  wash  bottle  shown  at  E  of  Fig.  5,  thus  completing  the  first 
step  of  the  analysis.  If  the  gas  being  analyzed  is  air,  the 
volume  after  treatment  with  KOH  should  be  the  same  as  before 
since  the  volume  of  C02  in  the  air,  0.04  per  cent.,  is  too  small  to 
be  measured  with  a  burette  of  this  type. 

In  the  practice  analysis  of  air  the  next  determination  would 
be  that  for  oxygen  which  would  be  absorbed  by  phosphorus 
or  alkaline  pyrogallate  as  directed  in  §§  3  and  4  of  Chapter  III. 
Air  contains  20. 9  per  cent,  of  oxygen  by  volume.  The  residue  is 
assumed  to  be  nitrogen. 

Successive  analyses  of  similar  gases  may  be  made  without 
changing  the  water  in  the  burette  provided  that  none  of  the 
reagents  have  been  carelessly  drawn  into  the  burette.  The 
greatest  danger  is  from  the  caustic  solution  which  will  absorb 
some  of  the  C02  from  a  newly  introduced  sample  before  its 
volume  has  been  measured.  Phenolphthalein  in  the  water 
will  show  when  it  has  become  alkaline  and  should  be  changed. 
There  is  no  objection  to  having  the  burette  water  faintly  acid 
and  there  is  the  advantage  that  small  amounts  of  alkali  are 
neutralized  and  rendered  harmless. 


GENERAL  METHODS  OF  TECHNICAL  GAS  ANALYSIS      27 

12.  Accuracy  of  the  Analysis. — Account  should  now  be 
taken  of  the  magnitude  of  various  possible  errors,  some  of 
which  have  not  been  mentioned.  The  smallest  division  on 
the  burette  is  usually  0.2  c.c.  and  the  volume  may  not  with 
certainty  be  estimated  by  interpolation  closer  than  0.1  c.c. 
This  probable  error  limits  the  accuracy  of  the  process  to  0.1  per 
cent,  with  a  sample  of  100  c.c.  and  an  accuracy  of  1.0  per  cent, 
with  a  sample  of  10  c.c.  Change  of  temperature  of  the  burette 
water  during  an  analysis  causes  a  change  of  0.36  per  cent,  in 
the  volume  of  the  gas  for  each  degree  centigrade.  Change  of 
barometric  pressure  causes  a  change  in  volume  of  0.13  per  cent, 
for  each  millimeter  of  mercury  change  in  pressure.  There  are 
other  minor  sources  of  error  which  will  be  mentioned  in  Chapter 
VI  under  "  Exact  Gas  Analysis."  It  will  be  evident  that  it  is 
perfectly  useless  to  expect  an  accuracy  of  greater  than  0.1  per 
cent,  with  apparatus  of  this  type,  and  that  an  error  of  0.2  per 
cent,  is  not  improbable.  An  analyst  who  reports  an  analysis 
carried  to  hundredths  of  a  per  cent,  only  shows  his  own  ignorance. 


CHAPTER  III 

ABSORPTION  METHODS  FOR  CARBON  DIOXIDE,  UN- 
SATURATED    HYDROCARBONS,    OXYGEN,    CARBON 
MONOXIDE  AND  HYDROGEN 

1.  Carbon  Dioxide.— This  gas  is  determined  by  absorption 
in  a  strong  solution  of  either  caustic  soda  or  potash.     Very 
concentrated  solutions  dry  the  gas  and  make  it  necessary  to 
let  it  stand  in  the  burette  before  reading  the  volume  until  it 
has  again  become  saturated  with  moisture.     Dilute  solutions 
work  too  slowly.     A  solution  of  50  grm.  NaOH  in  150  c.c.  of 
water  is  recommended  to  be  kept  in  the  form  0f  pipette  shown 
in  A  of  Fig..  8.     The  absorption  is  rapid,  three  minutes  being 
always   ample.     The   reaction  may   be   accelerated   by  gently 
shaking  the  pipette  or  by  passing  the  gas  back  and  forth.     Glass 
rods  or  perferably  glass  tubes  are  sometimes  introduced  into 
the  pipettes  to  accelerate  the  absorption  by  offering  a  large 
wetted  surface  with  which  the  gas  may  come  in  contact.     If 
this  device  is  used  care  must  be  taken  that  no  gas  bubbles  are 
trapped  in  the  pieces  of  glass  tubing  as  may  frequently  be  the 
case  if  they  are  less  than  5  mm.  internal  diameter  or  if  they  do 
not  stand  vertically.     If  it  is  desired  to  place  glass  tubes  in  the 
pipette  use  the  form  shown  in  B  of  Fig.  8.     It  will  be  necessary 
to  wire  the  rubber  stopper  firmly  into  place  to  prevent  leakage 
of  the  caustic. 

This  reagent  absorbs  not  only  carbon  dioxide  but  also  sulphur 
dioxide,  hydrogen  sulphide  and  any  other  acid  vapors  which 
may  be  present.  It  may  be  used  until  almost  all  of  the  caustic 
has  been  changed  to  carbonate.  One  pipette  will  absorb  about 
four  liters  of  C02-  There  will  be  slow  carbonate  formation 
through  exposure  to  the  air  but  the  reagent  may  be  used  with- 
out fear  for  several  months  provided  it  is  used  infrequently. 

2.  Unsaturated  Hydrocarbons. — These  gases  are  determined 
by  absorption  in  a  liquid  which  by  addition  forms  saturated 
compounds  from  the  unsaturated  ones.     In  gases  from  coal  the 

28 


ABSORPTION  METHODS  29 

predominating  constituent  is  ethylene,  C2H4,  but  smaller  per- 
centages of  the  other  olefines  are  present  and  sometimes  small 
amounts  of  acetylene,  C2H2.  A  solution  of  bromine  water 
made  by  diluting  one  volume  of  saturated  bromine  water  with  two 
volumes  of  water  is  the  reagent  preferred  by  the  author.  It  is 
placed  in  the  first  bulb  of  the  double  pipette  shown  in  C  of 
Fig.  8,  and  the  third  bulb  is  filled  with  water  to  lessen  the  diffu- 
sion of  bromine  into  the  air  of  the  laboratory.  If  the  solution 
becomes  bleached  through  formation  of  hydrobromic  acid  in  the 
sunlight,  it  is  sufficient  to  add  a  few  drops  of  liquid  bromine  which 
again  brings  it  up  to  its  normal  strength.  It  is  unnecessary  to 
have  it  so  strong  that  the  gas  drawn  back  into  the  pipette  shows 
pronounced  yellow  bromine  fumes.  When  gases  with  mor£ 
than  a  small  per  cent,  of  unsaturated  hydrocarbons  are  brought 
into  contact  with  bromine  it  is  possible  to  observe  the  formation 
of  the  bromide  as  an  oily  film  on  the  surface  of  the  liquid.  As 
this  film  retards  reaction  between  the  bromine  and  the  gas,  it  is 
advisable  to  shake  the  pipette  gently  during  absorption,  when 
little  drops  of  the  heavier  ethylene  bromide  may  be  seen  falling 
to  the  bottom  of  the  pipette.  The  gas  drawn  back  into  the 
burette  will  contain  so  much  bromine  vapor  that  its  volume 
may  even  have  increased . in  the  process.  It  must  be  passed  into 
a  caustic  solution  and  shaken  for  about  one  minute  to  remove 
the  bromine  fumes  and  then  brought  back  into  the  burette  and 
measured.  The  diminution  in  volume  is  to  be  reported  as 
unsaturated  hydrocarbons.  A  delicate  test  for  the  complete 
removal  of  these  constituents  is  afforded  when  phosphorus  is 
subsequently  used  as  a  reagent  for  oxygen.  A  fraction  of  a 
tenth  of  a  per  cent,  of  ethylene  will  completely  prevent  the 
reaction  between  phosphorus  and  oxygen.  Three  minutes 
shaking  with  the  bromine  is  sufficient  to  remove  the  unsaturated 
hydrocarbons  from  most  gases;  but  gases  of  high  candle  power, 
like  Pintsch  gas,  sometimes  require  ten  minutes.  Treatment 
with  bromine  water  should  be  repeated  until  phosphorus  smokes 
when  the  gas  is  brought  in  contact  with  it. 

Fuming  sulphuric  acid  acts  in  the  same  way  as  does  bromine 
water,  but  it  is  difficult  to  handle,  attacks  rubber  tubing  badly, 
and  must  be  protected  from  the  moisture  of  the  air  to  avoid  loss 
of  efficiency. 


30  GAS  AND  FUEL  ANALYSIS 

3.  Oxygen  by  Phosphorus. — Yellow  phosphorus  is  an  extremely 
reliable  reagent  for  the  absorption  of  oxygen  when  used  under 
proper  conditions.  It  combines  with  oxygen  producing  solid 
oxides  of  phosphorus  and  reacts  with  almost  no  other  gases 
which  might  be  present.  The  disadvantage  attending  its  use 
is  the  danger  of  the  reaction  not  taking  place  at  all  because 
of  the  presence  of  inhibiting  catalyzers,  because  of  too  low  tem- 
perature or  because  of  too  high  a  concentration  of  oxygen 
in  the  gas.  There  is,  however,  easy  ocular  evidence  of  the 
reaction  so  that  there  need  be  no  uncertainty  as  to  whether 
the  reaction  has  taken  place.  When  once  started  it  goes  to 
completion. 

The  pipette  is  of  the  form  shown  in  B  of  Fig.  8.  To  prepare 
it  for  use  the  pipette  is  inverted  and  filled  with  water  and  into 
it  are  dropped  sticks  of  phosphorus  about  5  mm.  in  diameter 
which  have  been  cut  to  proper  length  under  water.  The  sticks 
are  to  stand  vertically  and  fill  the  pipette  practically  full.  The 
only  advantage  of  the  small  sticks  lies  in  their  greater  surface 
and  in  the  convenience  with  which  the  pipette  may  be  filled.  It 
is  possible  to  prepare  them  in  the  laboratory  by  melting  phos- 
phorus under  water  at  a  temperature  a  little  above  44°  C.  and 
sucking  it  into  a  slightly  conical  glass  tube.  With  expert 
manipulation  this  tube  may  be  lifted  from  the  warm  water  and 
plunged  into  cold  water  where  the  phosphorus  will  soldify  and 
contract  so  that  the  stick  may  be  pushed  from  the  tube.  It  is 
simpler  though  not  so  elegant  to  mould  the  sticks  in  a  tin  dish 
about  5  in.  long  made  with  a  corrugated  bottom  and  provided 
with  a  rim  about  an  inch  high  and  a  handle.  This  mould 
is  submerged  in  "a  dish  of  warm  water  and  enough  phosphorus 
melted  in  it  to  fill  the  corrugations.  It  is  then  lifted  out  and 
placed  in  cold  water  till  the  sticks  become  solid.  Molten  phos- 
phorus catches  fire  instantly  in  the  air  and  produces  dangerous 
burns  on  the  skin.  Particles  of  solid  phosphorus  dropped  in 
cracks  of  a  wet  table  or  floor  have  been  known  to  smoulder 
twenty-four  hours  and  finally  burst  into  flame.  Great  care 
must  always  be  exercised  in  handling  phosphorus  and  it  is 
usually  preferable  to  buy  it  already  cast  in  small  sticks.  The 
pipette  should  be  kept  in  the  dark  when  not  in  use  to  avoid  the 
deterioration  of  the  phosphorus.  Pipettes  made  from  brown  glass 


ABSORPTION  METHODS  31 

retard  the  action  of  the  sunlight.  With  proper  care  a  phos- 
phorus pipette  should  last  for  years  without  refilling. 

When  a  gas  containing  oxygen  is  introduced  into  a  phosphorus 
pipette  there  normally  appears  at  once  a  dense  white  cloud  of 
oxides  of  phosphorus  which  are  evident  even  when  the  amount 
of  oxygen  is  less  than  0.1  per  cent,  of  the  total  volume.  All  tech- 
nical gases  will  contain  this  much  oxygen,  for  even  if  they  did 
not  contain  it  originally  they  will  have  absorbed  it  from  the  water 
of  the  sampling  apparatus  or  of  the  burette,  so  that  the  presence 
of  these  clouds  is  a  sure  indication  that  the  reaction  is  progressing 
properly.  Conversely  the  absence  of  any  smoke  means  not  that 
there  is  no  oxygen  present,  but  that  there  is  something  preventing 
the  reaction.  The  reaction  between  oxygen  and  phosphorus 
is  also  attended  by  a  glow,  visible  only  in  the  dark,  which  disap- 
pears with  the  completion  of  the  reaction.  The  white  cloud  con- 
sists of  solid  particles  of  phosphoric  oxides  which  slowly  settle  and 
dissolve  in  the  water.  It  is  not  necessary  to  wait  for  this,  how- 
ever, before  drawing  the  gas  back  into  the  burette  and  measuring 
the  oxygen  absorbed  for  the  particles  possess  very  slight  vapor 
tension  and  do  not  occupy  an  appreciable  volume.  The  reaction 
should  with  certainty  be  completed  in  three  minutes  if  the  white 
smoke  appears  promptly  and  if  the  surface  of  phosphorus  exposed 
is  large.  It  will  not  accelerate  the  reaction  to  shake  the  pipette 
since  the  reagent  is  a  solid  and  the  pipette  is  so  closely  filled 
with  sticks  that  diffusion  will  soon  bring  the  oxygen  to  the  sur- 
face of  the  phosphorus. 

The  sticks  of  phosphorus  at  first  yellow  and  waxy  become 
covered  with  a  reddish  crust  on  long  exposure  to  light  and  are  in- 
active. Such  sticks  may  be  melted  under  water,  skimmed,  and 
cast  into  new  sticks.  The  inactive  crust  may  also  be  removed 
by  placing  in  the  pipette  a  10  per  cent,  solution  of  K2Cr2O7 
made  faintly  acid  with  H2S04.  The  chromate  becomes  reduced 
to  the  green  chromic  salt  with  oxidation  of  the  surface  of  the 
phosphorus.  It  is  preferable,  however,  to  avoid  deterioration 
by  keeping  the  pipette  in  the  dark  when  it  is  not  in  use. 

If  the  white  vapors  do  not  appear  promptly  when  the  gas  is 
passed  into  the  pipette,  the  explanation  may  be  sought  in  four 
directions. 

a.  The  temperature  may  be  too  low.     It  should  be  above  15°  C. 


32  GAS  AND  FUEL  ANALYSIS 

b.  The  concentration  of  the  oxygen  may  be  too  high.     Moist 
phosphorus  does  not  react  at  all  with  perfectly  pure  oxygen  at 
ordinary  room  temperature.     If  the  partial  pressure  of  the  oxygen 
is  diminished  either  mechanically  by  an  air  pump  or  by  dilution 
with  an  inert  gas  the  reaction  commences.     With  50  per  cent, 
oxygen  it  is  violent,  flame  being  produced  and  the  phosphorus 
melting.     There  is  danger  of  breaking  the  pipette.     When  the 
concentration  is  less  than  30  per  cent,  the  reaction  proceeds 
quietly  and  the  phosphorus  does  not  melt. 

c.  An  inhibiting  catalyzer  may  be  present.     The  most  com- 
monly occurring  catalyzer  is  ethylene,  a  few  hundredths  of  a  per 
cent,  of  which  completely  prevents  the  reaction  between  phos- 
phorus and  oxygen.     Acetylene,  benzine,  ether,  hydrogen  sul- 
phide and  many  other  substances  possess  similar  though  usually 
weaker  powers.     Fortunately  they  are  practically  all  removed 
either  mechanically  or  chemically  by  bromine  water  followed  by 
caustic  potash  and  the  gas  should  always  be  thus  treated  if  the 
white  fumes  fail  to  appear  promptly. 

d..  The  phosphorus  may  have  been  rendered  inactive  by  a 
heavy  dose  of  a  catalyzer.  It  may  be  lestored  by  replacing  the 
water  in  the  pipette  with  fresh  water  and  passing  several  successive 
samples  of  air  into  the  pipette  until  the  phosphorus  again  smokes 
freely. 

Commercial  compressed  oxygen  should  be  diluted  with  nitro- 
gen before  analysis.  The  nitrogen  may  be  conveniently  pre- 
pared from  air  by  passing  a  buretteful  of  air  into  the  phosphorus 
pipette,  disconnecting  the  pipette  and  closing  it  with  a  pinchcock. 
Twenty-five  to  thirty  cubic  centimeters  of  the  oxygen  are  then 
to  be  drawn  into  the  burette  (note  that  a  calibration  error  of 
0.3  c.c.  means  1  per  cent,  here)  and  the  phosphorus  pipette  recon- 
nected. There  will  be  sufficient  nitrogen  in  it  to  flush  out  the 
capillary  connecting  tube  and  fill  the  burette  as  well.  The 
oxygen  may  now  be  absorbed  by  phosphorus.  It  is  desirable 
to  introduce  the  oxygen  into  the  burette  before  the  nitrogen 
which  thus  fills  the  upper  part  of  the  burette  and  comes  in  contact 
first  with  the  phosphorus.  If  the  reverse  procedure  were  fol- 
lowed and  the  oxygen  introduced  in  the  burette  last,  it  might 
be  brought  in  concentrated  form  in  contact  with  the  phosphorus 


ABSORPTION  METHODS  33 

and  cause  violent  combustion,  a  trouble  which  the  above  scheme 
of  procedure  avoids. 

4.  Oxygen  by  Alkaline  Pyrogallate. — This  reagent  is  very 
frequently  used,  especially  in  apparatus  of  the  Bunte  or  Orsat 
type.  When  used  with  proper  precautions  it  gives  accurate 
results.  Pyrogallol  is  a  trihydric  phenol  C6H3(OH)3  which  in 
alkaline  solution  is  a  strong  reducing  agent,  becoming  itself 
oxidized  to  other  products.  Unfortunately,  unless  the  solution 
is  freshly  prepared  and  strongly  alkaline  there  is  danger  of  carbon 
monoxide  being  evolved  as  oxygen  is  absorbed.  This  not  only 
causes  the  oxygen  to  be  reported  low,  but  also  makes  the  carbon 
monoxide  high.  Berthelot  has  shown  that  a  reagent  made  by 
taking  a  solution  of  1  part  of  pyrogallol  in  three  of  water  and 
mixing  it  with  its  own  volume  of  a  solution  of  1  part  of  KOH  in 
two  of  water  will,  when  freshly  prepared,  absorb  ten  times  its 
volume  of  oxygen  without  giving  back  more  than  a  trace  of  CO, 
but  that  solutions  which  have  been  used  too  long  or  do  not  con- 
tain enough  alkali  may  give  up  as  much  as  5  per  cent,  of  the 
volume  of  oxygen  absorbed  as  carbon  monoxide. 

The  reagent  should  be  kept  in  a  double  pipette  (C  of  Fig.  8), 
the  third  bulb  being  filled  with  water  to  prevent  action  of  the 
air  on  the  reagent.  It  may  also  be  kept  in  a  single  pipette 
(A  of  Fig.  8)  provided  a  rubber  balloon  is  fastened  to  the  second 
bulb  for  the  same  purpose.  The  reagent  works  very  slowly  at 
temperatures  below  15°  C.  Carbon  dioxide  and  other  gases 
which  would  be  absorbed  by  alkali  must  be  removed  before 
testing  for  oxygen  with  pyrogallate. 

Mr.  H.  A.  Small  in  the  author's  laboratory  tested  the  behavior 
of  a  solution  of  pyrogallate  made  up  according  to  Berthelot's 
directions  and  kept  in  an  ordinary  four  bulb  pipette  without 
any  special  precautions  to  prevent  diffusion  of  oxygen  into  the 
pipette.  Duplicate  samples  of  air  were  analyzed  , almost 
daily  for  more  than  a  month.  During  the  first  four  weeks  the 
reagent  absorbed  the  proper  percentage  of  oxygen  although 
it  was,  frequently  necessary  to  shake  more  than  three  minutes 
to  accomplish  this.  The  150  c.c.  of  reagent  in  the  pipette  had 
up  to  this  time  absorbed  1140  c.c.  of  oxygen.  After  this  the 
absorption  of  oxygen  became  incomplete,  the  line  of  demarca- 
tion being  quite  sharp  and  the  apparent  oxygen  of  the  air  drop- 


34  GAS  AND  FUEL  ANALYSIS 

ping  from  20.7  per  cent,  to  20.4  per  cent.  Tests  showed  that 
the  oxygen  was  still  being  quantitatively  absorbed  but  that 
about  0.3  per  cent,  of  carbon  monoxide  was  being  evolved. 
These  results  confirm  Berthelot's  statements.  According  to  our 
results  1  c.c.  of  the  reagent  absorbs  8.0  c.c.  of  oxygen.  In  case 
of  doubt  concerning  the  reagent  it  should  be  tested  on  air  and 
should  be  rejected  unless  it  absorbs  20.6  to  20.8  per  cent,  of  oxygen. 

5.  Other   Reagents   for   Oxygen. — Sodium   hydrosulfite   has 
been  recommended-by  Franzen-1  as  a  cheaper  and  better  reagent 
than  pyrogallol.     The  solution  is  prepared  by  dissolving  50  grm. 
Na2S204  in  250  c.c.  H2O  and  mixing  this  with  40  c.c.  of  a  caustic 
solution  made  by  dissolving  500  grm.  NaOH  in  700  c.c.  H2O. 
Each  cubic  centimeter  of  this  reagent  absorbs  10.7  c.c.  oxygen. 
The  equation  for  the  reaction  is  as  follows: 

Na2S204+ H2O  +  0  =  2NaHSO3 

The  solution  is  placed  in  a  pipette  containing  rolls  of  iron  gauze 
to  increase  the  absorbing  surface.  Franzen  states  that  the 
absorption  is  complete  in  five  minutes  without  shaking  and  pro- 
ceeds almost  as  rapidly  at  4°  C.  as  at  room  temperature. 
There  is  no  danger  of  the  formation  of  CO  in  the  process  which 
constitutes  the  greatest  objection  to  pyrogallate.  An  ammoni- 
acal  copper  solution  was  proposed  by  Orsat2  as  a  reagent  for 
the  absorption  of  oxygen.  He  used  a  cold  saturated  solution  of 
ammonia  and  ammonium  chloride  in  contact  with  metallic  cop- 
per. Oxygen  is  readily  absorbed  and  the  liquid  assumes  a  blue 
tint.  He  also  called  attention  to  the  limitation  in  the  use  of 
this  reagent  caused  by  the  action  of  the  ammoniacal  copper  salt 
on  carbon  monoxide. 

Oxygen  may  be  accurately  estimated  by  explosion  with 
•excess  of  hydrogen  or  by  combustion  with  copper  and  these 
methods  will  be  discussed  later. 

6.  Carbon  Monoxide. — The  methods  for  absorption  of  CO 
are  less  satisfactory  than  for  any  of  the  other  commonly  occurring 
gases.     The  usual  reagent  is  cuprous  chloride  Cu2Cl2  which  on 
account  of  its  slight  solubility  in  water  must  be  used  either  in 
acid  or  ammoniacal  solution.     The  acid  solution  consists  of  a 

1  Chem.-Berichte,  39,  2069  (1906). 

2  Annales  des  Mines,  1875,  490. 


ABSORPTION  METHODS  35 

practically  saturated  solution  of  cuprous  chloride  in  hydrochloric 
acid  of  specific  gravity  of  approximately  1.12.  Since  the  acid 
is  only  a  solvent,  its  exact  concentration  is  immaterial.  Com- 
mercial acid  may  be  used.  About  150  grm.  of  the  cuprous 
chloride  will  dissolve  in  a  liter  of  acid  of  this  concentration. 
This  solution  of  cuprous  chloride  when  pure  is  perfectly  colorless 
but  it  darkens  through  slight  oxidation  as  on  exposure  to  the 
air,  so  that  the  usual  solutions  are  black.  It  is  possible  to  keep 
it  colorless  by  placing  in  the  reagent  bottle  or  in  the  pipette 
copper  turnings  or  copper  wire,  but  it  does  not  increase  the 
efficiency  of  the  reagent.  If  the  oxidation  proceeds  so  far  that 
the  solution  becomes  green,  due  to  complete  oxidation  to  the 
cupric  state,  the  solution  is  worthless  until  it  is  again  reduced 
to  the  cuprous  state. 

The  reagent  is  kept  in  a  double  pipette  whose  third  bulb  is 
filled  with  HC1  of  sp.  gr.  1.12  instead  of  water  so  that  in  case 
the  cuprous  chloride  spills  into  it,  it  will  not  be  precipitated. 
The  gas  which  must  have  been  previously  freed  from  unsaturated 
hydrocarbons  and  oxygen  is  passed  into  the  pipette  and  shaken 
for  three  minutes,  then  drawn  back  to  the  burette  and  passed 
into  a  second  pipette  containing  fresh  cuprous  chloride  where 
it  is  again  shaken  for  three  minutes,  drawn  back  and  measured. 
The  HC1  vapors  in  the  gas  may  be  neglected.  There  is  no 
method  of  knowing  whether  the  absorption  of  the  CO  has  been 
complete.  The  only  safe  way  is  to  repeat  the  absorption  using 
a  fresh  solution  until  the  volume  becomes  constant.  Usually 
two  absorptions  of  three  minutes  each  are  sufficient. 

The  reaction  between  carbon  monoxide  and  cuprous  chloride 
has  not  been  definitely  worked  out.  Jones1  has  shown  that 
under  certain  circumstances  a  crystalline  compound  of  definite 
composition  results — Cu2Cl2,  2CO.  4H20.  In  the  dilute  solu- 
tions present  in  gas  analysis,  however,  the  reagent  behaves 
exactly  as  if  it  dissolved  the  carbon  monoxide.  When  a  perfectly 
new  solution  is  used  the  CO  will  be  practically  completely 
removed.  As  the  CO  in  solution  increases  there  comes  appar- 
ently an  equilibrium  between  that  in  the  gas  and  that  in  the 
solution,  with  the  result  that  the  absorption  is  incomplete.  If 
a  gas  with  only  a  small  amount  of  CO  is  brought  in  contact 

1  Am.  Chem.  Jour.,  22,  287. 

\ 
\ 


36  GAS  AND  FUEL  ANALYSIS 

with  a  solution  which  has  absorbed  much,  the  gas  will  increase 
in  volume  due  to  CO  given  up  by  the  solution.  Each  cuprous 
chloride  pipette  should  bear  a  label  on  which  should  be  recorded 
the  number  of  cubic  centimeters  of  carbon  monoxide  which  has 
been  absorbed.  When  it  has  absorbed  more  than  10  c.c.  it  is 
not  safe  to  rely  on  the  results.  In  practice  the  analyst  should 
have  two  pipettes  for  cuprous  chloride,  one,  which  has  absorbed 
considerable  carbon  monoxide,  to  be  used  first,  and  another, 
which  should  be  kept  almost  entirely  fresh  to  follow  the  other. 
When  this  second  pipette  has  absorbed  10  c.c.  of  CO  it  should 
be  used  as  the  first  pipette  and  the  former  first  pipette  should 
be  emptied  and  refilled  with  fresh  reagent.  The  solution  may 
be  regenerated  if  desired  by  boiling  it  for  half  an  hour  in  a  flask 
containing  some  metallic  copper  and  provided  with  a  reflux 
condenser  to  prevent  much  loss  of  acid.  The  feebly  held  CO  is 
driven  off  by  the  boiling  and  any  oxidized  solution  is  reduced  to 
the  cuprous  state  again. 

The  ammoniacal  solution  is  made  by  suspending  about  150 
grm.  of  cuprous  chloride  in  a  liter  of  distilled  water  into  which 
ammonia  gas  is  passed  until  the  liquid  becomes  a  pale  blue  color. 
The  ammoniacal  solution  slowly  regenerates  itself  on  standing, 
the  CO  becoming  oxidized  to  (NH4)2CO3  and  a  mirror  of  metallic 
copper  depositing.  The  NH3  gas  must  be  removed  by  an  acid 
pipette  before  the  correct  amount  of  CO  absorbed  may  be  read. 

Carbon  monoxide  may  be  estimated  by  explosion  or  combus- 
tion as  described  in  the  next  chapter.  Minute  amounts  of  it. 
may  be  estimated  by  the  I2O5  method  given  in  Chapter  VI  on 
"  Exact  Gas  Analysis." 

7.  Absorption  of  Hydrogen. — Hydrogen  may  be  absorbed  by 
palladium  sponge  superficially  oxidized  to  palladous  oxide, 
according  to  the  method  ot  Hempel.  It  is  necessary  to  re- 
generate the  palladium  after  each  experiment  and  the  reaction 
is  prevented  by  small  amounts  of  carbon  monoxide,  hydrochloric 
acid  and  other  constituents  so  that  it  is  not  a  method  which  has 
found  much  favor. 

A  solution  of  palladous  chloride  as  prepared  by  Campbell  and 
Hart1  is  a  better  reagent.  It  is  used  as  an  almost  neutral  1  per 
cent,  solution  prepared  by  dissolving  5  grm.  palladium  wire  in 

lAm.  Chtm.  Jour.,  18,  294  (1896). 


ABSORPTION  METHODS  37 

30  c.c  of  HC1  to  which  is  added  1  or  2  c.c.  HN03.  The  solution 
thus  prepared  is  evaporated  just  to  dry  ness  on  the  water  bath, 
redissolved  in  5  c.c.  of  HC1  (sp.  gr.  1.20)  and  25  or  30  c.c.  of 
water,  warmed  till  solution  is  complete  and  diluted  to  750  c.c. 
It  is  placed  in  a  simple  Hempel  pipette  made  to  be  readily 
detachable  from  its  frame  so  that  the  bulbs  may  be  placed  in  a 
water  bath.  The  first  bulb  of  the  pipette  should  have  a  capacity 
of  at  least  150  c.c.  to  allow  for  expansion  of  the  gas  and  water 
vapor  when  the  solution  is  warmed.  The  gas  freed  by  the  usual 
methods  from  CO2,  CnH2n,  O2  and  CO,  and  containing  H2, 
CH4  and  N2  is  passed  into  the  pipette  and  the  water  from  the 
burette  passed  over  to  seal  the  capillary  of  the  pipette.  A  screw 
clamp  is  placed  on  the  rubber  connecting  tube  and  the  pipette 
disconnected  from  the  burette  and  placed  in  a  water  bath  at 
50°  C.  for  an  hour  and  a  half.  A  higher  temperature  does  no 
harm  provided  it  does  not  expand  the  gas  so  much  as  to  cause 
it  to  bubble  out  of  the  first  bulb  or  to  leave  only  a  small  amount 
of  reagent  in  contact  with  the  gas  in  the  first  bulb.  The  hydrogen 
reacts  with  the  palladium  chloride  forming  metallic  palladium 
and  HC1.  The  total  decrease  in  volume  is  reported  as  hydrogen. 
The  reagent  may  be  counted  on  to  absorb  one-third  of  its  volume 
of  hydrogen  completely  in  an  hour  and  a  half.  Larger  quanti- 
ties will  be  absorbed  more  slowly.  It  is  readily  regenerated  by 
rinsing  from  the  pipette,  evaporating  just  to  dryness  on  the 
water  bath,  dissolving  in  5  or  6  c.c.  HC1  and  4  or  5  drops  of 
HNOs  and  again  evaporating.  The  dry  palladous  chloride  is 
dissolved  by  adding  2  c.c.  cone.  HC1  and  a  small  amount  of 
water  and  is  then  diluted  to  its  original  volume.  The  method 
is  accurate  and  satisfactory.  Carbon  monoxide  and  other 
reducing  gases  behave  like  hydrogen  and  must  be  removed  pre- 
vious to  the  test  but  hydrocarbons  of  the  methane  series  are 
not  affected.  The  chief  objection  to  the  method  lies  in  the  time 
consumed  which  makes  it  frequently  necessary  to  correct  the 
gas  volumes  for  change  in  room  temperature  and  barometric 
pressure.  A  memorandum  should  be  made  of  the  temperature 
of  the  burette  jacket  and  of  the  barometric  pressure  before  and 
after  the  test  and  corrections  made  if  necessary. 

Paal    and    Hartmann1    recommend    a    solution    of    colloidal 

1  Chem.  Berichte,  43,  243  (1910).  "  ••«.  £ 


38  GAS  AND  FUEL  ANALYSIS 

palladium  made  by  dissolving  2.44  grm.  collodial  palladium 
manufactured  according  to  Paai's  process  by  Kalle  (  =  1.5  grm. 
palladium)  and  2.74  grm.  of  sodium  picrate  in  enough  water  to 
bring  the  volume  to  130  c.c.  Gaseous  hydrogen  dissolves  in  the 
aqueous  palladium  solution  and  reduces  the  picric  acid.  Hempel l 
has  made  a  critical  study  of  this  method  and  reports  that 
a  solution  prepared  in  this  manner  will  absorb  in  15  minutes 

when  freshly  prepared  21.2  c.c.  H2  per  1  c.c.  reagent, 
after  79  days  16.2  c.c.  H2  per  1  c.c.  reagent, 

after  1  year  1.6  c,c.  H2  per  1  c.c.  reagent. 

He  states  that  a  fresh  solution  may  be  safely  trusted  to  absorb 
completely  7.2  c.c.  H2  per  centimeter  reagent  in  three  minutes 
if  heated  to  the  temperature  of  the  blood.  He  advocates  the 
preparation  of  the  solution  in  small  quantities  and  its  use  in  a 
pipette  filled  mainly  with  mercury.  A  disadvantage  attending 
the  use  of  the  reagent  is  the  persistent  foam  which  results  after 
shaking  and  which  must  be  allowed  to  subside  before  the  volume 
of  the  gas  is  read.  A  few  drops  of  alcohol  at  once  dissipate 
the  foam  but  spoil  the  reagent  for  further  use.  When  alcohol  is 
used  the  pipette  must  be  carefully  cleaned  before  another 
experiment. 

In  using  this  method  the  gas  must  first  be  freed  from  oxygen 
which  is  caused  to  unite  with  the  hydrogen  by  the  palladium, 
from  unsaturated  hydrocarbons  which  form  addition  products 
with  the  hydrogen,  and  from  carbon  monoxide  which  retards 
the  absorption  of  the  hydrogen.  Bromine  is  recommended  as 
the  absorbent  for  the  unsaturated  hydrocarbons  as  it  removes 
compounds  of  arsenic  and  phosphorus  which  might  retard  the 
catalytic  action.  Alkaline  pyrogallate  is  advised  for  absorption 
of  oxygen  as  phosphorus  fumes  affect  the  palladium.  An 
ammoniacal  solution  of  copper  chloride  is  preferred  to  the  acid 
solution. 

8.  General  Scheme  of  Analysis. — Fig.  9  shows  the  apparatus 
ready  for  the  analysis.  The  details  concerning  the  individual 
steps  of  the  process  were  given  in  Chapter  II  but  it  is  well  to 
recapitulate  the  important  points  in  connection  with  the  general 

1Zeit.  Angewandt.  Chem.,  25,  1843  (1912). 


ABSORPTION  METHODS 


39 


scheme  of  analysis.  The  water  of  the  burette  is  saturated  with 
gas  similar  to  that  which  is  to  be  analyzed  and  a  sample  of  ap- 
proximately 100  c.c.  is  then  drawn  in  and  the  volume  read  at 
atmospheric  pressure  after  three  minutes  have  been  allowed  to 
elapse  so  that  the  surplus  water  will  have  drained  from  the  bur- 
ette walls.  Any  needed  correction  for  burette  error  is  to  be 
applied  to  this  reading.  The  caustic  soda  pipette  is  to  be  con- 


r 


FIG.  9. — Assembled  apparatus  for  gas  analysis.         > 

nected  to  the  burette,  and  the  gas  passed  into  it  and  allowed  to 
remain  with  gentle  shaking  for  three  minutes.  C02  is  absorbed, 
as  well  as  H2S,  SO2  etc.,  the  whole  being  usually  reported  as  CO2. 
The  gas  is  drawn  back  into  the  burette  and  while  waiting  for  the 
excess  water  on  the  burette  walls  to  run  down,  the  capillary 
connecting  tube  is  flushed  out  and  the  bromine  water  pipette 


40  GAS  AND  FUEL  ANALYSIS 

is  connected.  The  volume  in  the  gas  burette  is  then  read,  and 
the  gas  passed  into  the  bromine  water  where  it  is  shaken  for  three 
minutes.  It  is  drawn  back  to  the  burette,  and  at  once  passed 
into  the  caustic  pipette  where  it  is  shaken  one  minute  to  re- 
move bromine  fumes.  It  is  then  drawn  back  into  the  burette 
and  the  decrease  in  volume  reported  as  unsaturated  hydrocar- 
bons. The  gas  is  next  passed  into  the  phosphorus  pipette. 
White  smoke  at  once  appears.  If  it  does  not,  it  is  a  sign  that 
some  retarding  catalyzer  is  present,  usually  removable  by  an- 
other treatment  with  bromine  water.  Following  the  estimation 
of  oxygen  comes  that  of  carbon  monoxide  with  cuprous  chloride 
either  acid  or  ammoniacal,  preferably  acid  unless  hydrogen  is 
to  be  absorbed  by  palladium.  Two  cuprous  chloride  pipettes 
must  be  used  in  series,  the  second  one  containing  almost  fresh 
reagent.  The  residue  from  this  absorption  consists  of  hydrogen, 
hydrocarbons  of  the  paraffine  series  and  nitrogen.  The  hydrogen 
may  be  absorbed  by  palladium  as  outlined  in  this  chapter  but  it 
is  more  common  practice  to  estimate  the  hydrogen  and  hydro- 
carbons by  combustion.  The  methods  are  discussed  in  the  next 
chapter. 


CHAPTER  IV 

EXPLOSION  AND  COMBUSTION  METHODS  FOR 

HYDROGEN,  METHANE,  ETHANE 

AND  CARBON  MONOXIDE 

1.  Available  Methods. — Hydrogen  and  carbon  monoxide  may 
be  estimated  by  absorption  as  indicated  in  the  preceding  chapter. 
They  may  also  be  estimated  after  oxidation  to  water  or  carbon 
dioxide.  There  are  no  satisfactory  absorbents  for  methane  and 
ethane  and  so  these  gases  are  always  estimated  indirectly  after 
oxidation.  The  oxidizing  agent  may  be  gaseous  oxygen  and  the 
reaction  may  be  violent  as  in  explosion  methods  or  it  may  be 
quiet  combustion.  There  may  even  be  combustion  of  hydrogen 


Platinum 
Wire, 
Fused  in- 

Wall 

Stop  Cock,  2mm. 
Bore 

*3 mm.  Infernal 

Diameter 

FIG.  10. — Detail  of  explosion  pipette. 

and  carbon  monoxide  with  the  aid  of  a  catalyzer  in  the  presence 
of  methane  which  remains  unchanged.  The  oxidizing  agent  may 
also  be  an  oxide,  especially  copper  oxide,  and  here  again  there 
may  be  fractional  combustion.  The  most  rapid  method  and 
the  one  most  frequently  used  is  that  of  explosion. 

2.  Apparatus  for  Explosion  Analysis. — The  analysis  by  ex- 
plosion is  carried  out  in  a  stout  glass  vessel  provided  with  elec- 
tric connections  across  whose  terminals  a  spark  may  be  passed 
to  cause  the  explosion.  The  shape  and  dimensions  of  the  appa- 
ratus may  vary.  The  form  which  has  given  good  satisfaction 

41 


42  GAS  AND  FUEL  ANALYSIS 

in  the  gas  laboratory  at  the  University  of  Michigan  for  a  number 
of  years1  is  shown  in  Fig.  10.  It  is  a  modification  of  the  Hempel 
pipette  and  differs  from  it  principally  in  the  arrangement  of  the 
electric  terminals  and  in  the  incorporation  of  an  explosion  guard 
in  the  stand. 

In  the  older  forms  of  pipette  the  explosion  was  induced  by  a 
spark  made  to  jump  a  gap  between  two  platinum  wires  sealed 
through  the  glass  of  the  narrowed  upper  part  of  the  bulb.  When 
the  interior  of  the  bulb  became  wet  as  frequently  happened  the 
electric  current  would  sometimes  travel  around  the  wet  wall 
instead  of  sparking  across  the  gap,  and  it  was  not  possible  to 
obtain  an  explosion.  Gill2  modified  the  bulb  by  introducing  one 
of  the  wires  through  a  ground  glass  joint  at  the  bottom  of  the 
pipette.  This  was  a  valuable  modification  because  it  made 
the  creeping  distance  so  long  that  the  spark  was  compelled  to 
jump  the  gap,  but  the  ground  glass  was  difficult  to  keep  tight. 
The  form  here  described  introduces  the  wire  from  the  bottom  but 
adopts  a  simple  method  of  sealing  which  is  very  satisfactory. 
The  lower  wire  which  should  be  stiff  (and  may  be  of  nickel  about 
1  mm.  in  diameter)  is  pushed  through  the  open  lower  end  of 
the  pipette  and  sealed  by  sucking  molten  sealing  wax  into  the 
pipette  almost  to  the  level  of  the  tee.  As  the  sealing  wax 
hardens  the  wire  may  be  moved  to  adjust  the  spark  gap  to  the 
desired  dimensions.  No  difficulty  has  been  experienced  in 
making  this  joint  tight.  The  explosion  pipette  and  its  stand 
are  shown  in  Fig.  11.  The  bulb  is  enclosed  in  a  box  open  at 
the  top  and  with  a  plate  glass  window  in  front,  so  that  the 
operator  can  observe  the  explosion  in  perfect  safety.  The  bot- 
tom of  this  box  has  an  irregular  opening  sawed  in  it  so  that  the 
pipette  as  shown  in  Fig.  10  may  be  lowered  into  place.  The  bulb 
sits  in  a  cup  shaped  hollow  of  the  shelf  which  may  be  padded 
with  wet  asbestos  paper  if  necessary  to  make  it  fit  well. 

The  weight  of  the  mercury  renders  other  fastening  for  the  bulb 
unnecessary  but  the  capillary  is  fastened  to  the  rib  behind  it  by 
a  loop  of  fine  copper  wire  passing  through  holes  drilled  in  the  rib. 
The  strain  of  the  rubber  tube  filled  with  mercury  is  taken  off  the 
glass  tee  by  a  ring  below  the  shelf  into  which  the  rubber  tube  is 

1  White  and  CampbeU,  J.  Am.  Chem.  Soc.,  27,  734  (1905). 
*J.  Am.  Chem.  Soc.,  17,  771  (1895). 


EXPLOSION  AND  COMBUSTION  METHODS 


43 


wedged  firmly  by  a  split  cork.  The  rack  for  the  levelling  bottle 
is  higher  than  the  tee  of  the  pipette  so  that  when  the  bottle  is  in 
the  rack  the  mercury  in  the  rubber  tube  is  under  pressure  whereas 
if  the  mercury  bottle  were  sitting  on  the  base  of  the  stand  there 
would  be  a  partial  vacuum  within  the  rubber  tube.  This  may 
seem  immaterial,  but  it  must  be  remembered  that  all  rubber  is 
porous  and  that  bubbles  of  air  sucked  into  the  rubber  tube  are 
certain  to  make  their  way  up  into  the  pipette  and  be  measured 


FIG.  11. — Explosion  pipette  and  stand  with  protecting  screen. 

as  part  of  the  gas  in  it.  Fine  copper  wires  soldered  to  the  elec- 
trode terminals  of  the  pipette  pass  to  the  binding  posts  on  the 
stand.  The  fine  platinum  electrode  is  liable  to  be  cut  if  it  is 
bent  back  and  forth  where  it  is  sealed  through  the  glass  and  to 
protect  it  the  copper  wire  from  the  upper  electrode  is  brought 
smoothly  up  to  the  capillary  and  tied  there  firmly  with  thread. 
The  design  of  the  stand  is  such  that  if  a  bulb  breaks  a  new  bulb 
may  be  inserted  without  trouble  if  it  has  even  approximately  the 
dimensions  of  the  old  one.  The  method  of  connecting  this  pipette 
to  the  burette  and  of  transferring  the  gas  is  the  same  as  for  other 


44  GAS  AND  FUEL  ANALYSIS 

pipettes.  This  pipette  is  filled  with  mercury,  since  under  the 
high  pressure  developed  the  solubility  of  the  gases  in  water 
becomes  large  enough  to  cause  appreciable  error.  An  induction 
coil  capable  of  giving  a  half  inch  spark  together  with  its  bat- 
tery is  necessary.  A  coil  giving  a  large  spark  such  as  is  given 
by  the  automobile  sparkers  is  much  better  than  a  coil  giving  a 
thin  high  voltage  spark. 

3.  Manipulation  in  Explosion  Analysis. — In  the  explosion  proc- 
ess a  sample  of  gas  previously  freed  from  carbon  dioxide,  oxygen, 
unsaturated  hydrocarbons  and  usually  carbon  monoxide  is  drawn 
into  the  burette  and  measured.  Its  volume  may  vary  from  8.0 
c.c.  with  pure  methane  to  50  c.c.with  gases  containing  high  per- 
centages of  nitrogen.  .  Air  sufficient  to  fill  the  burette  is  then 
drawn  in.  The  burette  is  connected  to  the  pipette  as  usual, 
care  being  taken  to  have  the  rubber  connections  in  good  condition 
and  firmly  wired,  and  the  mixture  is  passed  into  the  explosion 
pipette,  the  water  of  the  burette  being  run  over  through  the  cap- 
illary of  the  pipette  until  the  capillary  is  full.  This  water  in  the 
capillary  acts  as  a  cushion,  preventing  the  force  of  the  explosion 
from  blowing  up  the  rubber  connections.  The  gas  in  the 
explosion  pipette  is  brought  to  atmospheric  pressure  by  means 
of  the  levelling  bottle,  the  stopcock  is  closed,  and  the  levelling 
bottle  replaced  in  its  rack.  It  is  advisable  to  shake  the  pipette  to 
ensure  thorough  mixing  of  the  gases,  for  diffusion  proceeds  some- 
what slowly.  The  gas  is  exploded  by  a  spark  from  the  induction 
coil.  If  the  gas  consists  mainly  of  hydrogen  there  is  usually 
no  visible  flame  although  a  slight  tremor  of  the  mercury  may  be 
observed.  If  the  gas  contains  much  hydrocarbon  a  flash  of  flame 
may  usually  be  seen.  It  is  not  advisable  to  spark  the  mixture 
more  than  a  second  as  some  nitrogen  will  unite  with  the  oxygen 
at  the  temperature  of  the  spark  forming  oxides  of  nitrogen  with 
decrease  of  volume  and  erroneous  results.  The  explosion  com- 
pleted, the  gas  is  again  brought  to  atmospheric  pressure  by  means 
of  the  levelling  bottle,  and  then  brought  back  into  the  burette  and 
measured.  If  there  has  been  marked  contraction,  the  next  step 
is  to  pass  the  gass  into  caustic  solution  and  determine  if  there 
has  been  formation  of  carbon  dioxide. 

If  the  decrease  in  volume  after  explosion  was  less  than  12 
c.c.  it  is  almost  certain  that  the  explosion  was  incomplete.  If 


EXPLOSION  AND  COMBUSTION  METHODS  45 

there  was  no  decrease  in  volume  it  is  not  safe  to  assume  that  no 
combustible  gas  was  present,  for  it  may  have  been  present  in  such 
a  small  proportion  that  the  mixture  was  not  explosive.  The 
proper  procedure  in  either  case  is  to  add  about  10  c.c.  of  pure 
hydrogen  made  by  the  action  of  caustic  potash  on  metallic 
aluminum  and  explode  a  second  time.  The  addition  of  this 
amount  of  hydrogen  ensures  complete  explosion.  After  allow- 
ance for  the  contraction  due  to  the  added  hydrogen,  the  composi- 
tion of  the  original  gas  may  be  calculated  as  explained  later. 

It  is  advisable  to  determine  roughly  the  amount  of  oxygen 
remaining  after  the  explosion  so  that  there  may  be  no  doubt 
that  an  excess  was  present. 

^4.  Oxidation  of  Nitrogen  as  a  Source  of  Error. — Almost  all 
technical  gases  contain  nitrogen  as  do  also  commercial  forms  of 
oxygen.  Bunsen  first  noted  that  nitrogen  and  oxygen  react  at 
the  temperature  of  the  electric  spark  or  of  an  explosion  flame  to 
form  small  amounts  of  various  oxides  of  nitrogen  whose  volume 
is  less  than  that  of  the  reacting  gases  and  which  combine  with 
caustic.  The  formation  of  oxides  of  nitrogen  leads,  therefore,  to 
an  erroneously  high  contraction  after  explosion  and  to  an  errone- 
ously high  figure  for  C02  due  to  explosion.  The  error  is  discussed 
more  fully  in  Chapter  VI  on  Exact  Gas  Analysis  but  it  cannot  be 
altogether  neglected  in  technical  work.  The  error  increases  with 
higher  flame  temperatures  and  the  simplest  way  to  keep  it  within 
reasonable  limits  is  to  dilute  the  reacting  gases  with  some  inert 
gas  such  as  nitrogen  or  excess  of  oxygen.  The  volume  of  the 
gases  participating  in  the  explosion  (combustible  gas  -f  theoret- 
ical volume  oxygen)  should  be  from  one-third  to  one-fifth  that 
of  the  non-exploding  gases  (nitrogen  +  excess  oxygen).  It  will 
be  seen  that  12  c.c.  H2+  6  c.c.  O2  require  to  be  diluted  with  from 
54  to  90  c.c.  nitrogen  or  oxygen  and  that  8  c.c.  CH4  +  16  c.c. 
C>2  require  at  least  72  c.  c.  of  diluting  gases. 

The  explosion  of  large  samples  of  gas  mixed  with  commercial 
oxygen,  a  method  proposed  by  Hinman  and  endorsed  by  Gill,1 
involves  much  greater  danger  of  blowing  up  the  pipette  and  be- 
cause of  the  higher  temperature  of  explosion,  tends  to  cause 
a  larger  formation  of  oxides  of  nitrogen  from  the  nitrogen 
necessarily  present. 

1  J.  Am.Chem.  Soc.,  17,  987  (1895). 


46  GAS  AND  FUEL  ANALYSIS 

5.  Accuracy  of  Explosion  Methods. — The  necessity  of  diluting 
the  exploding  gases  to  avoid  oxidation  of  nitrogen  restricts  the 
size  of  a  sample  of  a  rich  gas  like  illuminating  gas  to  about  10 
c.c.     With  this  small  sample  each  0.1  c.c.  error  in  reading  means 
1.0  per  cent.     A  greater  accuracy  can  therefore  not  be  expected 
except  by  averaging  a  number  of  analyses.     It  may  be  considered 
safe  to  rely  upon  a  single  analysis  for  the  various  gases  deter- 
mined by  absorption,  but  explosion  analyses  should  always  be 
made  in  duplicate.     The  main  portion  of  the  gas  after  the 
absorption  should  be  stored  in  a  gas  holder  to  be  drawn  upon  for 
subsequent  check  analyses. 

6.  Hydrogen  by  Explosion. — If  hydrogen  is  the  only  com- 
bustible gas  taking  part  in  the  explosion  its  volume  may  be 
calculated  from  the  contraction  after  explosion  according  to 
the  following  equation: 

2H2+02  =  2H20 
2+1  =2  or  0 

Expressed  in  volumes  this  means  that  two  volumes  of  hydrogen 
combine  with  one  volume  of  oxygen  to  form  two  volumes  of 
water  vapor.  Since,  however,  the  gas  after  explosion  cools 
again  to  the  temperature  of  the  burette  water  and  is  the  same 
as  before  explosion,  and  since  it  was  saturated  with  water 
before  explosion,  the  additional  water  formed  must  all  condense. 
For  our  purposes,  therefore,  two  volumes  of  H2  react  with  one 
volume  of  02  with  complete  disappearance  of  the  reacting  gases. 
Under  these  circumstances  when  hydrogen  is  the  only  exploding 
gas,  two-thirds  of  the  resulting  contraction  will  be  the  volume 
of  the  hydrogen  exploded. 

7.  Hydrogen  and  Methane  by  Explosion. — Methane  combines 
with  two  volumes  of  oxygen  to  form  carbon  dioxide  and  water 
according  to  the  following  equation: 

CH4+202  =  C02+2H20 

1+2      =   1  .  +  0 

The  volumetric  relations  are  expressed  by  the  figures  of  the 
equation,  one  volume  of  methane  uniting  with  two  of  oxygen 
to  form  one  volume  of  carbon  dioxide,  and  two  of  water  vapor 


EXPLOSION  AND  COMBUSTION  METHODS  47 

which  condense  and  disappear  as  explained  in  the  preceding 
paragraph.  The  result  of  the  explosion,  therefore,  is  that  there 
is  a  contraction  of  two  volumes  for  every  one  volume  of  methane 
and  the  formation  of  a  volume  of  carbon  dioxide  equal  to  the 
methane. 

It  is  possible  to  determine  the  proportion  of  hydrogen  and 
methane  present  in  a  gas  mixture  by  explosion  with  air.  The 
volume  of  carbon  dioxide  resulting  from  the  explosion  equals 
the  volume  of  the  methane.  The  contraction  due  to  the  methane 
is  twice  the  volume  of  the  methane  and  the  difference  between 
this  contraction  in  volume  and  the  total  contraction  is  the 
contraction  due  to  the  explosion  of  hydrogen.  In  accordance 
with  the  preceding  section  two-thirds  of  this  contraction  is 
hydrogen.  The  following  example  will  serve  as  an  illustration 
of  the  method  of  calculation.  ' 


Sample  of  illuminating  gas 99 . 5      c.c. 

Volume  after  absorption  of  CO2,  CnH2n,  O2,  CO 85 . 2 

Sample  for  explosion 10.3 

Air  to 97.6 

After  explosion,  volume 80 . 1 

Contraction 17.5 

After  KOH,  volume 74.9 

Vol.  CO2  formed 5.2 

After  phosphorus,  volume 69 . 4 

Vol.  excess  oxygen 5.5 

Calculation  5 . 2  c.c.  CO2  =  5 . 2  c.  c.  CH4 

Contraction  due  to  5.2  c.c.  CH4  =  2X5.2  =  10.4 
Contraction  due  to  hydrogen  =17.5  =  10.4  =  7.1 
Hydrogen      =    2/3X7.1=4.7 
Vol.     CH4     =    5.2 
Vol.       H2     =    4.7 
Vol.  N2by  diff.  0.4 


10.3 


Per  cent.  CH4  =  5.2Xi 

Percent.   H2    _4.7x|g£g^-39.0 

Per  cent.   N2    =0.4Xin  Vvoa  ^=  3<3 


48  GAS  AND  FUEL  ANALYSIS 

The  ratio  of  exploding  to  non-exploding  gases  in  the  above 
illustration  may  be  calculated  as  follows: 

Exploding  gases  5.2  c.c.     CH4-f  10.4  c.c.     O2  =  15.6 
4.7c.c.       H2+2.35c.c.     O2  =  7.05 


Exploding  gases  22.65 

Non-exploding  gases  97 . 6  -  22 . 65  =  74 . 95 

exploding_gases         22.65  _     1 
non-exploding  gases     74. 95  ~~  3^3 

The  excess  of  oxygen  is  calculated  from  the  volume  of  air 
taken  for  explosion,  =97.6-10.3  =  87.3  c.c.  air  with  20.9  per 
cent.  O2=  18.24  c.c.  O2  available.  Used  for  combustion, 
as  above,  10.4+2.35  =  12.75  c.c.  Excess  oxygen  =  18.24- 
12.75  =  5.49  c.c.,  which  checks  with  the  5.5  c.c.  found  by  direct 
experiment. 

8.  Carbon  Monoxide,  Hydrogen  and  Methane  by  Explosion.  — 
The  composition  of  a  gas  mixture  containing  CO,  H2,  and  CH4 
may  be  determined  by  a  single  explosion  if  in  addition  to  the 
contraction  and  C02  the  oxygen  used  in  the  explosion  is  also 
determined. 

There  are  various  methods  of  calculation,  that  given  by 
Noyes  and  Shepherd1  being  as  follows: 

1.  Gas  taken  =  CH4+CO+H2+N2 

2.  Contraction  =2CH4+JCO+|H2 

3.  Oxygen  consumed  =2CH4+|CO+iH2 

4.  CO2  formed  =  CH4+CO 

Hence      H2  =  Contraction  —  02  consumed. 
C0  =  |  (2C02+iH2-O2  consumed) 
CH4  =  C02-CO 

N2  =  Total  gas-(H2+CO+CH4). 

The  oxygen  consumed  is  calculated  by  determining  the  residual 
oxygen  and  deducting  this  from  the  volume  of  oxygen  introduced 
as  air  whose  percentage  of  oxygen  is  assumed  to  be  20.9. 

This  method  is  more  rapid  than  the  usual  one  in  which  the 
CO  is  absorbed  by  Cu2Cl2,  and  it  has  no  systematic  errors, 
provided  the  dilution  is  great  enough  to  avoid  oxidation  of 
nitrogen.  It  will,  except  in  expert  hands,  be  found  less  reliable 

1  /.  Am.  Chem.  Soc.  20,  345  (1898). 


EXPLOSION  AND  COMBUSTION  METHODS 


49 


than  the  usual  method  of  absorption  of  CO  and  explosion  of  H2 
and  CH4  because  each  value  calculated  is  dependent  on  the 
accuracy  of  three  successive  operations  instead  of  two. 

9.  Quiet  Combustion  of  a  Mixture  of  Oxygen  and  Combust- 
ible Gas. — Various  attempts  have  been  made  to  do  away  with 
the  explosion  pipette  by  causing  the  gas  to  burn  gradually. 
Coquillion1  in  1876  proposed  to  estimate  small  amounts  of 
hydrocarbons  in  the  air  from  mines  by  placing  within  a  pipette 
a  spiral  of  platinum  or  palladium  wire.  The  mine  air  was  in- 
troduced into  the  pipette,  the  spiral  was  to  be  heated  to  redness 
and,  the  amount  of  combustible  gas  being  below  the  explosive 
ratio,  the  hydrocarbons  were  to  be  gradually  burned.  He 
recommended  that  for  technical  gases  where  there  was  danger 
of  explosion  the  platinum  spiral  be  placed  in  a  small  bulb  blown 


FIG.  12. — Quartz  combustion  tube  with  platinum  spiral. 

in  the  capillary  tube  between  the  burette  and  pipette.  The 
mixture  of  gas  and  air  was  measured  in  the  burette,  and  then 
passed  through  the  capillary  over  the  glowing  spiral.  The 
capillary  tube  was  supposed  to  be  adequate  to  prevent  the 
explosion  from  flashing  back  into  the  burette.  Hempel2  has 
improved  this  latter  apparatus  by  placing  the  platinum  spiral 
in  a  quartz  tube  between  two  glass  capillary  tubes.  His  arrange- 
ment as  modified  by  the  author  is  shown  in  Fig.  12  where  AB 
represents  a  tube  of  transparent  quartz  about  4  mm.  internal 
diameter  and  125  mm.  long,  at  each  end  of  which  are  glass  cap- 
illary tees  connected  to  it  by  rubber  tubing.  Through  each  tee 
runs  a  stout  nickel  wire  connected  by  a  spiral  of  fine  platinum 
wire.  The  nickel  wires  are  sealed  into  the  glass  capillaries  by 
sealing  wax  drawn  into  the  enlarged  ends  of  the  capillaries.  The 
apparatus  may  therefore  be  readily  repaired  if  the  platinum 

1  Comptes  rendus,  83,  394;  84,  458  and  1503. 

2  Zeit.  angewandt.  Chem.,  25,  1841  (1912). 

4 


50  GAS  AND  FUEL  ANALYSIS 

wire  becomes  burned  out.  The  nickel  wires  should  be  so  large 
that  they  almost  fill  the  capillary  tube  which  should  be  of  about 
1  mm.  internal  diameter.  They  will  then  not  be  heated  per- 
ceptibly by  the  passage  of  an  electric  current  sufficient  to  heat 
the  platinum  wire  to  redness  and  will  by  their  cooling  action 
help  to  prevent  the  explosion  from  flashing  back  into  the  gas 
burette.  If  the  mixture  of  gas  and  air  is  passed  slowly  over  the 
platinum  spiral  the  temperature  will  not  rise  above  a  fair  red 
heat  and  there  will  be  little  danger  of  formation  of  oxides  of 
nitrogen,  hence  there  is  no  need  of  diluting  the  gases  with  so 
much  air  as  is  necessary  in  the  explosion  process  and  therefore  a 
larger  sample  of  gas  may  be  used.  It  is  not  safe,  however,  to 
take  a  large  sample  of  gas  and  dilute  it  with  pure  oxygen,  for  the 
capillary  tube  cannot  be  relied  upon  to  prevent  an  explosion 
flashing  back  into  the  burette  when  a  very  explosive  mixture  is 
used. 

The  inaccuracy  of  the  usual  explosion  methods  led  Dennis 
and  Hopkins1  to  devise  a  process  of  combustion  whereby  a 
large  sample  of  gas  might  be  quietly  burned  in  pure  oxygen. 
The  combustion  pipette  consists  of  a  pipette  such  as  is  used  for 
phosphorus  with  its  second  bulb  cut  off  and  a  levelling  bottle 
for  mercury  connected.  The  ignition  wire  in  the  form  of  a 
platinum  coil  or  grid  is  placed  within  the  pipette  immediately 
under  the  gas  inlet  and  connected  to  two  heavy  wires  which, 
insulated  from  each  other,  pass  through  the  rubber  stopper  at 
the  bottom  of  the  pipette  and  are  fastened  to  binding  posts. 
The  diameter  and  length  of  the  platinum  ignition  wire  must  be 
chosen  with  reference  to  the  electric  circuit  so  that  it  will  be 
easily  heated  to  redness  and  its  temperature  controlled  without 
the  need  of  cumbrous  rheostats.  The  conducting  wires  within 
the  pipette  may  be  of  platinum  or  one  of  the  non-rusting  nickel- 
chromium  alloys  and  should  be  at  least  1  mm.  in  diameter. 

The  manipulation  is  as  follows.  The  full  volume  of  gas 
remaining  after  absorption  of  oxygen,  consisting  of  CO,  H2, 
CH4  and  N2  is  transferred  to  the  combustion  pipette  and  a 
clamp  is  screwed  onto  the  rubber  connecting  tube  at  the  tip  of 
the  burette  so  that  the  pipette  may  be  disconnected  from  the 
burette.  The  burette  is  filled  with  oxygen  free  from  CO2  and 

1  J.  Am.  Chem.  Soc.,  21,  398  (1899). 


EXPLOSION  AND  COMBUSTION  METHODS  51 

of  known  purity  and  reconnected  to  the  pipette,  but  the  stop- 
cock of  the  burette  is  kept  closed.  The  levelling  bottle  of  the 
pipette  is  placed  at  such  a  height  that  the  gas  in  the  pipette  is 
under  slightly  diminished  pressure  and  the  electric  ignition  wire 
brought  to  incandescence.  The  stopcock  on  the  burette  is 
now  opened  and  a  slow  stream  of  oxygen  passed  into  the  pipette. 
A  slight  flash  is  usually  noticeable  as  ignition  takes  place  and 
the  platinum  wire  glows  more  brightly  so  that  it  may  be  necessary 
to  interpose  more  resistance  in  the  heating  circuit.  The  volume 
of  gas  in  the  pipette  may  either  increase  or  decrease  and  the 
height  of  the  levelling  bottle  must  be  varied  accordingly.  It  is 
usually  necessary  to  periodically  increase  the  external  resistance 
to  prevent  the  platinum  wire  from  burning  out  as  the  hydrogen 
originally  present  gives  way  to  water  vapor.  After  the  oxygen 
is  all  passed  into  the  pipette,  the  current  is  interrupted,  the  gases 
allowed  to  cool  and  the  CO,  H2  and  CH4  determined  as  in  §  8. 

The  great  advantage  of  this  process  Hes  in  the  large  sample 
and  the  consequent  diminution  of  the  error  of  observation.  It 
requires  a  special  pipette,  which  is,  however,  easily  constructed, 
a  source  of  electric  current  and  a  controlling  rheostat.  The 
manipulation  is  somewhat  complicated  and  it  has  been  the 
author's  experience  that  novices  usually  wish  that  nature  had 
provided  them  with  an  extra  pair  of  hands.  The  error  due  to 
oxidation  of  nitrogen  has  been  found  by  the  author1  to  be  fully 
as  large  in  this  process  as  in  the  explosion  process.  The  subject 
is  discussed  more  fully  in  Chapter  VI.  Hempel2  also  reports 
unfavorably  on  this  process  on  account  of  the  formation  of  oxides 
of  nitrogen  when  combustion  is  continued  long  enough  to  ensure 
oxidation  of  all  the  methane. 

10.  Fractional  Combustion  with  Palladinised  Asbestos. — The 
well  known  power  of  palladium  to  bring  about  the  union  of  hy- 
drogen and  oxygen  at 'low  temperature  has  long  been  made  use 
of  as  a  means  of  separating  hydrogen  from  methane.  The  use 
of  palladinised  asbe^cs,  is  due  to  Winkler.  The  asbestos  is 
prepared  by  soaking  &  small  amount  of  selected  long  fibered 
asbestos  in  a  concentrated  solution  of  palladous  chloride  prepared 
according  to  §  7  of  Chapter  III.  The  fibers  are  to  be  kept  as 

1  J.  Am.  Chem.  Soc,  23,  477  (1901). 
2Zeit.  Angewandt.  Chtrn.,  25,  1841  (1912). 


52  GAS  AND  FUEL  ANALYSIS 

nearly  parallel  as  possible  and  after  saturation  are  to  be  dried 
and  ignited  at  a  very  dull  red  heat  when  the  chloride  will  de- 
compose leaving  the  fibers  coated  with  metallic  palladium  and 
possibly  palladous  oxide.  A  bundle  of  two  or  three  of  these 
single  fibers  about  an  inch  long  is  introduced  into  the  end  of  a 
straight  capillary  glass  tube  about  1  mm.  internal  diameter  and 
eight  inches  long,  and  brought  to  the  middle  of  the  capillary  by 
suction  on  the  opposite  end  of  the  tube.  A  drop  of  water  on 
the  asbestos  makes  it  move  more  freely.  The  capillary  is  then 
to  be  dried  and  bent  to  the  usual  form  for  connecting  the  burette 
and  pipette. 

In  manipulation  20  or  30  c.c.  of  gas  freed  from  CO2,  CnH2n 
and  usually  CO  is  mixed  with  an  excess  of  air  and  passed  through 
the  capillary  tube  containing  the  palladinised  asbestos  into  a 
pipette  containing  water.  If  the  asbestos  is  very  active,  com- 
bustion may  begin  without  external  heat  but  to  make  certain 
the  tube  is  heated  with,a  small  gas  flame  or  alcohol  lamp.  It  is 
not  necessary  to  heat  the  tube  to  redness.-  A  spark  frequently 
appears  at  the  end  of  the  asbestos  filament  when  the  combustible 
gas  first  strikes  it.  This  is  a  sign  that  the  gas  is  passing  too 
rapidly  and  the  speed  must  be  decreased  until  the  spark  disap- 
pears. Otherwise  some  methane  will  be  burned.  The  gas  is 
passed  back  and  forth  through  the  capillary  twice  and  then  drawn 
back  into  the  burette  and  the  volume  measured.  If  hydrogen 
alone  has  been  burned  two-thirds  of  the  contraction  will  be  the 
volume  of  the  hydrogen  as  explained  in  §  6.  Carbon  monoxide 
will  burn  as  well  as  hydrogen  in  this  process  and  where  both 
were  present,  it  will  be  necessary  to  determine  the  carbon  dioxide 
formed  in  addition  to  the  contraction.  The  calculations  follow 
from  the  equations  : 

2CO  +  02  =  2CO2 

2  +  1       =2  Contraction  =  JCO  or 

2H2+02  =  2H2O 

2+1    =0  Contraction  =  |H2 


ThereforeCO2  = 

Total  contraction  =  iCO+|H2 
H2  =  f  (contraction  -  |CO) 


EXPLOSION  ANI>'$&MBUSTION  METHODS  53 

This  method  is  accurate  provided  the  palladinised  asbestos 
is  dry  and  active  and  the  proper  temperature  is  maintained. 
It  requires  care  to  prevent  any  drops  of  water  from  getting  into 
the  capillary.  If  this  happens  when  the  capillary  is  cold  the 
thread  of  asbestos  becomes  wet  and  must  be  dried  thoroughly 
before  it  is  active.  If  a  drop  of  water  gets  into  the  capillary 
while  it  is  hot  the  glass  tube  cracks.  Very  little  attention  has 
been  paid  to  the  possibility  of  small  amounts  of  foreign  gases 
rendering  the  palladium  catalyzer  inactive,  but  from  the  elaborate 
precautions  which  are  necessary  to  keep  the  platinum  contact 
substance  active  in  the  sulphuric  acid  manufacture  it  is  evident 
that  this  possibility  should  not  be  ignored.  The  capillary  tube 
should  never  be  heated  to  redness  on  account  of  danger  of  burn- 
ing methane.  The  combustible  gases  are  diluted  largely  with 
air  to  avoid  too  intense  combustion  and  also  to  avoid  an  ex- 
plosion of  the  main  body  of  the  gas  which  might  be  propagated 
through  the  capillary  if  the  gas  mixture  were  too  rich.  Dis- 
astrous explosions  have  been  known  to  result  from  an  attempt 
to  burn  mixtures  of  hydrogen  and  oxygen  in  this  manner.  The 
combined  volumes  of  hydrogen  and  carbon  monoxide  in  the 
sample  taken  for  analysis  should  not  be  over  20  c.c.  and  the 
volume  after  dilution  with  air  should  be  almost  100  c.c.  This 
method  has  been  investigated  by  Nesmjelow1  who  emphasizes 
the  danger  of  burning  methane  if  the  gases  are  passed  through 
the  capillary  at  a  rate  faster  than  one  liter  per  hour.  Hempel2 
has  recently  reported  the  results  of  a  study  of  this  process  and 
finds  that  to  obtain  accurate  results  the  temperature  of  the 
capillary  must  not  rise  over  400°  C.  and  that  the  gas  must  be 
passed  at  a  speed  of  not  over  100  c.c.  in  eight  minutes.  He  rec- 
ommends, as  a  method  of  temperature  control,  that  the  portion 
of  the  capillary  to  be  heated  rest  in  a  brass  trough  which  in  the 
middle  is  thickened  sufficiently  to  contain  a  hole  deep  enough 
for  a  thermometer  bulb.  In  default  of  a  thermometer  a  glass 
tube  sealed  at  the  bottom  and  containing  a  little  mercury  may 
be  inserted  in  the  hole.  The  boiling  of  the  mercury  (358° 
C.)  indicates  when  a  sufficiently  high  temperature  has  been 
reached. 

1  Zeit.  Anal.  Chem.,  48,  232  (1909). 

2  Zeit.  Angewandt.  Chem.,  25,  1841  (1912). 


54  GAS  AND  FUEL  ANALYSIS 

11.  Fractional  Combustion  with  Copper  Oxide. — The  com- 
bustion of  carbon  compounds  of  all  sorts  through  contact  with 
hot  copper  oxide  has  been  a  method  long  employed  by  organic 
chemists.  Campbell1  first  utilized  the  principle  of  fractional 
combustion  in  gas  analysis  and  determined  accurately  the  mini- 
mum combustion  temperature  for  various  gases  both  with  copper 
oxide  alone  and  with  palladinised  copper  oxide.  His  values 
are  as  follows: 


Gas 

Initial  combustion  point 

Pure  CuO                            Pd.-CuO 

H2...  

175-180°  C. 
100-105°  C. 
315-325°  C. 
270-280°  C. 
320-330°  C. 
Nc  combustion  at  455°  C. 

80-85°  C. 
100-105°  C. 
240-250°  C. 
220-230°  C. 
270-280°  C. 

CO                         

C2H4 

C3H6 

C4H8  (Iso)         

CH4  

Jaeger2  first  proposed  a  convenient  scheme  for  utilizing  this 
principle  in  ordinary  gas  analysis  and  the  method  usually  bears 
his  name.  He  takes  advantage  of  the  wide  difference  in  the 
ignition  point  of  CO  and  H2  as  compared  with  CH4  to  separate 
the  two  gases  by  fractional  combustion.  His  method  with  some 
modifications  which  the  author  has  found  desirable  is  as  follows: 

The  combustion  tube  shown  at  A  in  Fig.  13  is  of  hard  Jena 
glass  or  preferably  transparent  quartz  and  has  an  internal 
diameter  of  about  10  mm.  and  a  length  of  200  mm.  It  is  filled 
throughout  its  middle  100  mm.  with  granulated  copper  oxide 
kept  in  place  by  wads  of  asbestos  fiber.  The  open  ends  of  the 
tube  are  closed  by  elbows  of  glass  capillary  tubing  which  slip 
within  each  end  of  the  combustion  tube  as  far  as  the  asbestos 
wads  and  are  held  in  place  by  rubber  tubing  fitting  tightly  over 
the  end  of  the  combustion  tube  and  also  over  the  glass  capillary. 
The  asbestos  shield  shown  in  section  at  B  and  in  elevation  at  C 
sits  like  a  saddle  over  the  middle  portion  of  the  tube  and  keeps 
the  heat  from  the  rubber  connections  during  combustion. 
The  combustion  gases  pass  out  the  perforations  shown  in  the 
top  of  the  shield.  A  thermometer  standing  in  the  tube  of  the 

lAm.  Chem.  Jour.,  17,  688  (1895). 
9 Jour.  Gasbeleucht,  41,764  (1898). 


EXPLOSION  AND  COMBUSTION  METHODS 


55 


shield  with  its  bulb  touching  the  combustion  tube  indicates 
the  temperature  at  which  hydrogen  is  being  burned. 

The  whole  volume  of  the  gas  from  which  CO2,  CnH2n  and  02 
have  been  removed  is  used  for  the  analysis.  The  copper  oxide 
tube  is  connected  to  the  burette  on  one  side  and  on  the  other  to 
a  phosphorus  pipette  which  has  been  previously  filled  with  air 
and  now  contains  nitrogen.  This  nitrogen  is  allowed  to  flow 
through  the  combustion  tube  and  out  into  the  air  through  the 
burette  stopcock  flushing  out  the  air  in  the  tube  and  rendering 


FIG.  13. — Quartz  combustion  tube  filled  with  copper  oxide. 

unnecessary  the  troublesome  correction  involved  in  Jaeger's 
original  method.  The  nitrogen  is  all  driven  out  of  the  phos- 
phorus pipette,  and  the  water  in  it  blown  to  a  mark  arbitrarily 
fixed  on  the  capillary  stem  of  the  pipette  and  the  burette  stop- 
cock turned  so  that  connection  with  the  outside  air  is  shut  off, 
the  burette  also  remaining  closed.  The  gas  burner  under  the 
combustion  tube  is  lighted  and  adjusted  so  that  the  thermometer 
inserted  in  the  jacket  and  resting  on  the  combustion  tube  shows 
about  250°  C.  The  expanding  nitrogen  in  the  combustion 
tube  is  free  to  pass  into  the  phosphorus  pipette.  When  the 


56  GAS  AND  FUEL  ANALYSIS 

combustion  tube  is  hot,  the  burette  stopcock  is  opened  and 
the  gas  passed  slowly  into  the  phosphorus  pipette  and  back 
again  so  that  it  has  all  been  exposed  twice  to  the  action  of  the 
copper  oxide.  A  few  cubic  centimeters  of  the  gas  are  again 
passed  into  the  phosphorus  pipette,  the  burette  stopcock  is 
closed  and  the  flame  removed.  If  the  combustion  tube  is  of 
glass  it  must  be  slowly  cooled  to  room  temperature  but  if  it  is 
of  quartz  it  may  be  sprayed  with  water  or  wrapped  with  a  wet 
cloth  until  it  again  reaches  room  temperature.  As  the  tube 
cools  there  is  sucked  back  from  the  pipette  some  of  the  gas 
purposely  placed  there  and  when  it  is  thought  that  the  tube 
has  reached  room  temperature  the  liquid  of  the  pipette  is  again 
brought  to  the  mark  in  the  capillary  which  was  used  at  the  com- 
mencement of  the  test.  If  after  adjustment  has  been  made  the 
water  of  the  pipette  continues  to  rise  in  the  capillary  it  is  proof 
that  the  combustion  tube  has  not  yet  reached  room  temperature. 
The  volume  of  the  gas  in  the  burette  is  now  measured  and  a 
caustic  potash  pipette  substituted  for  the  phosphorus  pipette. 
This  requires  somewhat  careful  manipulation  for  the  combustion 
tube  is  still  filled  with  gas  which  must  not  be  allowed  to  diffuse 
into  the  air.  To  accomplish  the  substitution  the  stopcock  of 
the  burette  is  opened  and  the  gas  drawn  out  of  the  capillary 
of  the  phosphorus  pipette  into  the  burette  until  the  liquid  has 
mounted  as  high  as  the  rubber  connecting  tube.  The  glass 
capillaries  of  the  pipette  and  the  combustion  tube  are  separated 
enough  to  allow  a  clamp  to  be  screwed  on  the  rubber  tube  and 
the  phosphorus  pipette  is  disconnected  and  replaced  by  a  caustic 
pipette  whose  liquid  before  making  the  connection  is  blown 
practically  to  the  top  of  the  capillary  by  the  help  of  a  rubber 
tube  attached  to  the  second  bulb.  With  care  this  substitution 
of  one  pipette  for  the  other  may  be  made  with  an  error  of  only  a 
few  tenths  of  a  cubic  centimeter.  The  carbon  dioxide  formed 
from  the  CO  is  then  determined.  Since  it  is  not  feasible  to  drive 
all  the  gas  from  the  combustion  tube  into  the  caustic  the  gas 
should  be  passed  back  and  forth  several  times.  The  method 
of  calculation  of  the  H2  and  CO  follows  from  the  equations: 


CO+CuO  =  CO2+Cu 


EXPLOSION  AND  COMBUSTION  METHODS  57 

The  metallic  copper  has  practically  the  same  volume  as  the 
copper  oxide.  The  CO2  has  the  same  volume  as  the  CO.  The 
H2  completely  disappears.  Therefore  the  contraction  in  volume 
after  heating  to  250°  is  equal  to  the  H2,  and  the  C02  is  equal  to 
the  CO. 

Methane  is  estimated  by  heating  the  combustion  tube  to 
redness  and  slowly  passing  the  gas  back  and  forth  into  the 
caustic  pipette.  Methane  burns  somewhat  slowly  and  it  is 
wise  to  pass  it  back  and  forth  at  least  four  times.  The  decrease 
in  volume  is  read  after  the  combustion  tube  has  been  cooled 
as  before.  The  equation  for  the  reaction  is: 

CH4+4CuO  =  4Cu+C02+2H2O. 

If  the  gas  had  been  passed  back  and  forth  into  a  pipette  filled 
with  water  during  the  combustion  there  would  have  been  no 
change  in  volume  but  since  the  gas  was  passed  into  the  caustic 
pipette  during  the  combustion  process  and  the  C02  was  absorbed 
the  contraction  equals  the  methane. 

It  is  assumed  in  this  calculation  that  CH4  is  the  only  one  of 
the  paraffine  series  present.  This  is  usually  the  case  but  natural 
gas,  Pintsch  gas,  carburetted  water  gas  and  gas  from  coal  dis- 
tilled below  a  red  heat  may  contain  small  proportions  of  ethane 
and  possibly  higher  homologues.  Pentane  vapors  are  present 
in  many  samples  of  natural  gas.  Any  two  constituents  such  as 
methane  and  ethane  may  be  determined  by  this  method  if  during 
the  combustion  at  a  red  heat  the  gases  are  passed  back  and  forth 
into  the  phosphorus  pipette  or  other  pipette  filled  simply  with 
water  and  the  contraction  after  combustion  measured  and  then 
the  C02  determined.  The  calculation  follows  from  the  equations : 

CH4+4CuO  =  4Cu+C02+2H2O. 
C2H6+7CuO  =  7Cu+2CO2+3H20. 

In  the  case  of  CH4,  the  volume  is  the  same  after  combustion 
as  before.  In  the  case  of  C2H6  the  volume  has  increased  by  a 
volume  of  C02  equal  to  the  C2H6.  Any  increase  in  volume  after 
combustion  is  reported  as  C2H6  and  the  volume  of  the  C02  less 
twice  the  C2H6  is  reported  as.  CH4. 

In  case  pentane  is  present  the  increase  of  volume  after  com- 


58  GAS  AND  FUEL  ANALYSIS 

bustion  is  four  volumes  for  each  volume  of  pentane  according  to 
the  equation — 

C5H12+ IGCuO  =  5CO2+6H2O. 

It  is  not  usually  feasible  to  distinguish  by  analysis  between 
the  various  higher  hydrocarbons. 

The  copper  oxide  has  been  partially  reduced  to  metallic  copper 
in  the  combustion  and  must  be  re-oxidized  by  drawing  air  through 
the  red  hot  tube.  This  may  be  done  very  conveniently  by  means 
of  an  aspirator  since  no  attention  on  the  part  of  the  analyst  is 
required. 

This  method  is  perhaps  the  most  accurate  of  the  technical 
methods  for  the  estimation  of  CO,  H2  and  CH4  and  is  to  be  com- 
mended because  it  does  not  involve  any  special  equipment 
which  cannot  be  made  by  the  analyst  himself.  It  is  somewhat 
slower  than  the  explosion  methods  but  if  a  quartz  tube  is  available 
it  is  not  a  tedious  process.  A  quartz  tube  is  highly  desirable  since 
glass  tubes  always  break  after  a  time  and  in  breaking  usually 
spoil  the  analysis.  There  is  no  danger  of  oxidation  of  nitrogen 
as  in  the  other  methods  and  a  large  sample  of  gas  may  be  taken 
thus  reducing  the  errors  of  observation  to  a  minimum.  The 
greatest  liability  to  error  comes  from  incomplete  combustion  of 
the  hydrocarbons.  Ethane  is  especially  difficult  to  burn  and 
it  is  desirable  to  repeat  the  combustion  on  the  gas  residue  after 
the  CO2  has  been  absorbed  to  make  sure  that  there  is  no  further 
formation  of  C02. 

12.  Nitrogen. — There  is  no  desirable  method  for  the  direct 
determination  of  nitrogen,  which  is  always  taken  by  difference. 
This  is  very  unsatisfactory  since,  although  some  of  the  errors 
in  analysis  may  compensate  each  other,  there  is  a  tendency  in  a 
long  analysis  for  them  to  pile  up  on  the  nitrogen. 

The  Jaeger  method  of  combustion  with  copper  oxide  just 
described  allows  all  of  the  gases  other  than  nitrogen  to  be  re- 
moved in  a  single  process  and  affords  a  valuable  check  on  the 
accuracy  of  the  longer  anaylsis.  A  sample  of  100  c.c.  of  the  gas 
to  be  analyzed  is  passed  through  the  combustion  tube  at  red 
heat  and  into  caustic.  The  CO2>  CO,  H2,  and  CnHm  will  all 
disappear  in  the  process  as  will  also  the  oxygen  if  it  is  present  in 


EXPLOSION  AND  COMBUSTION  METHODS  59 

only  small  amount.     The  residue  will  be  nitrogen  and  possibly 
oxygen  which  may  be  removed  by  phosphorus. 

13.  Form  of  Record  of  Gas  Analysis. — There  may  of  course 
be  great  variation  in  methods  of  keeping  records  of  gas  analyses. 
The  record  should  in  every  case  however  be  full  enough  to  show 
every  step  of  the  operation.  The  following  record  is  given  as  a 
sample. 

ANALYSIS  OF  ILLUMINATING  GAS 

at  Chemical  Laboratory,  University  of  Michigan,  Sept.  9,  1907 

Sample  99.4-0.3=99.1  c.c. 

After  KOH  97.4  CO2          =2.0  c.c.  =2.0% 

After  Br2  92.6  C2H4,  etc.,  4.8  c.c.      4.8 

After  P  92.2  O2  0.4  c.c.      0.4 

After  Cu2Cl2  84.8-0.3=84.5  CO  7.4  c.c.      7.5 

First  explosion: 

Sample  9.4-0.3=  9.1 

Air  to  97.9-0.3=97.6 

After  explosion  83.0                                     Contraction  =14.9 

After  KOH  79.2                                                    CO2=  3.8 

After  P  71.0                                     Excess  O2      =8.2 

Calculations : 

Factor  to  give  percentage  Q  ^^99 r  j  =9.37 

CH4  =  3.8X9.37  =35.6% 

H2  =2/3(14. 9-2X3. 8)9. 37     =45.6% 

N2  =  [9.1-(3.8+4.87)]9.37    =  4.0% 

Exploding  gases: 

3.8  c.c.  CH4+7.6  c.c.  O2         =11. 4  c.c. 

4. 9  c.c.     H2+2.4c.c.  O2       =  7.3  c.c. 


18.7 

Non-exploding  gases: 
97.6-18.7  78.9 

non-exploding     78.9 
Ratl°       exploding 1^7=4-2 

Second  explosion: 

Sample  9.2—0.3=  8.9  c.c. 

Air  to  95.0-0.3=94.7 

After  explosion  80 . 4                       Contraction  14 . 6 

After  KOH  76.7                      CO2                 3.7 

After  P  70.0                      Excess  O2       6.7 


60 

Calculations : 


GAS  AND  FUEL  ANALYSIS 


Factor  to  give  percentage    -  =9.58 


CH4  =3.7X9.58  =35.4% 

H2  =2/3(14.6-2X3.7)9.58       =46.0 

N2  =[8.  9-(3.  7+4.8)]9.58         =  3.8 

Exploding  gases: 

3.7  c.c.  CH4+7.4  c.c.  O2  =  ll.l  c.c. 
4.8c.c.     H2+2.4  c.c.  O2=  7.2 


Non-exploding  gases: 
94.7-18.3 


Ratio 


non-exploding 
exploding 


18.3 

=  76.4 

^76.4 
~18.3 


'4.2 


Summary  of  analysis: 

I  II 

CO2  2.0 

C2H4,  etc.,  4.8 

O2  0.4 

CO  7.5 

CH4  35.6                 35.4 

H2  45.6                46.0 

N2  4.0                  3.8 


Average 

2.0% 
•  4.8 

0.4 

7.5 
35.5 
45.8 

3.9 


99.9% 


CHAPTER  V 

VARIOUS  TYPES  OF  APPARATUS  FOR  TECHNICAL  GAS 

ANALYSIS 

1.  Introduction. — Chapter  II  describes  the  apparatus  which 
the  author  believes  best  adapted  to  technical  gas  analysis  and 
gives  detailed  directions  for  its  manipulation.     The  present  chap- 
ter will   describe  various  other  forms  of  technical  apparatus 
especially  those  which  first  embodied  valuable  principles.     The 
number  of  modifications  is  legion  and  no  attempt  will  be  made  to 
even  enumerate  them.     The  order  of  description  will  in  general  be 
historical. 

2.  Schlosing  and  Rolland's  Apparatus. — Perhaps  the  earliest 


FIG.  14. — Schlosing  and  Rolland's  apparatus. 

successful  attempt  to  devise  an  apparatus  for  the  rapid  analysis 
of  industrial  gas  was  that  of  Schlosing  and  Holland1  who  de- 
vised a  simple  apparatus  which  foreshadowed  closely  the  modern 
type.  Their  apparatus  apparently  attracted  little  attention 
1  Annales  de.  Chim.,  Series  4,  t.14,  55  (1868). 

61 


62  GAS  AND  FUEL  ANALYSIS 

partly  because  its  description  was  embodied  in  a  long  article  on 
the  ammonia-soda  process  whose  title  did  not  contain  any  ref- 
erence to  gas  analysis.  The  original  cut  of  their  apparatus  is 
reproduced  as  Fig.  14  as  it  still  may  serve  as  a  model  for  a  chemist 
who  has  to  improvise  his  own  apparatus.  The  following  descrip- 
tion of  the  apparatus  is  taken  from  the  original  work.  In  the 
upper  left  hand  corner  of  the  cut  are  seen  four  lead  pipes  of  small 
diameter  coming  from  various  pieces  of  apparatus  in  the  plant.  A 
rubber  tube  d  connects  any  one  of  these  with  the  copper  tube  t 
to  which  is  attached  an  aspirator.  The  burette  a  terminates  at 
the  top  in  a  tee  of  almost  capillary  tubing,  one  arm  of  which  con- 
nects to  the  gas  supply  through  the  cock  r  and  the  other  to  the 
pipette  b.  No  mention  is  made  of  a  clamp  on  the  rubber  tube 
between  a  and  b  but  necessarily  such  must  have  been  used.  To 
draw  a  sample  of  gas  the  cock  r  is  opened  and  the  levelling  bottle 
c  is  raised  until  the  water  fills  the  burette  and  reaches  r.  The 
gas  formerly  in  the  burette  is  now  in  the  pipe  t  out  of  which  it  is 
swept  by  the  stream  of  gas  which  is  constantly  flowing.  The 
bottle  is  then  lowered  until  the  gas  has  passed  below  the  100  mark. 
The  aspirator  is  stopped,  the  rubber  tube  d  disconnected  and  the 
bottle  raised,  r  being  again  opened  until  the  level  of  the  water  in 
the  burette  is  at  100  and  is  at  the  same  time  coincident  with  the 
level  of  the  water  in  the  levelling  bottle.  The  burette  will  then 
contain  100  volumes  of  gas  at  atmospheric  pressure.  The  gas 
is  then  passed  back  and  forth  into  the  absorption  pipette  b  filled 
with  caustic  potash  and  containing  glass  tubes  to  increase  the 
absorptive  surface.  The  volume  in  the  burette  is  then  read  as 
before  and  the  decrease  in  volume  reported  as  GO2. 

3.  Orsat's  Apparatus. — The  original  form  of  the  Orsat1  appa- 
ratus is  practically  the  same  as  that  frequently  used  today,  as 
will  be  seen  by  Fig.  15  which  is  a  reproduction  of  the  original  cut. 
It  consists  of  a  water-jacketed  gas  burette  terminated  at  its  upper 
end  by  a  branched  glass  capillary  tube.  The  pipettes,  in  order 
from  right  to  left,  contain  caustic  potash,  alkaline  pyrogallate  and 
cuprous  chloride.  The  cock  I  on  the  branched  capillary  serves 
for  the  connection  of  a  platinum  capillary  in  which  hydrocarbons 
mixed  with  air,  and  added  hydrogen  if  necessary,  may  be  burned. 
The  sample  of  gas  is  brought  to  the  burette  by  the  water-aspira- 

1  Annales  des  Mines,  Series  7,  t.8,  485  (1875). 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS 


63 


tor  KLM  which  sucks  a  rapid  stream  of  gas  through  the  cock  R 
and  the  dust  filter  P.  The  operation  of  the  apparatus  will  be 
evident  to  anyone  who  has  read  the  three  preceding  chapters. 

Many  modifications  of  this  burette  have  been  prepared  since 
it  was  first  described,  but  the  principle  has  not  been  altered.  One 
group  of  workers  has  increased  the  complexity  of  the  apparatus  in 
an  attempt  to  increase  speed  of  manipulation.  The  most  note- 
worthy change  of  this  sort  is  probably  the  introduction  of  the 


FIG.  15. — Orsat  apparatus.     Original  form. 

bubbling  pipette  in  which,  by  a  three-way  cock  on  the  top  of  each 
pipette,  the  gas  is  made  to  pass  down  a  central  tube  and  bubble  up 
through  the  liquid  of  the  pipette  to  be  later  drawn  from  the  top  of 
the  pipette  when  the  three-way  cock  is  thrown  to  its  second  posi- 
tion. There  are  decided  objections  to  complication  in  any  form 
of  apparatus  which  may  receive  rough  treatment  in  transportation 
and  which  is  frequently  handled  carelessly  by  its  operators. 

The  usual  modifications  of  the  Orsat  apparatus  possess  at  least 
four  glass  stopcocks  on  the  various  outlets  of  the  branched  tee. 


64 


GAS  AND  FUEL  ANALYSIS 


Unless  the  apparatus  is  always  manipulated  by  a  skilled  operator 
it  is  almost  inevitable  that  some  of  the  alkaline  reagent  from  the 
pipettes  will  be  drawn  into  these  stopcocks.  It  is  apparently 
equally  inevitable  that  the  cocks  will  as  a  consequence  stick  and 
become  broken.  The  branched  tee  is  itself  a  source  of  trouble 
since  it  is  fragile  and  difficult  to  clean  when  stopped.  In  Fig. 
16  is  shown  a  modification  of  the  Orsat  apparatus  due  to  Allen  and 

Moyer  which  commends  itself 
for  its  simplicity  and  durability. 
The  capillary  glass  tube  is  re- 
placed by  one  of  hard  rubber  and 
the  glass  stopcocks  are  replaced 
by  pinchcocks  which  are  practi- 
cally as  satisfactory.  The  pip- 
ettes themselves  are  of  the  test 
tube  type  and  are  closed  at  the' 
top  with  a  soft  rubber  stopper 
which  is  pressed  against  the 
upper  shelf  by  the  screw  which 
supports  the  cup  in  which  each 
pipette  rests.  This  gives  a  firm 
and  yet  elastic  support  for  the 
pipettes  which  prevents  breakage 
Allen-  in  shipment. 

The  method  of  operating  all 
Orsat  burettes  is  the  same.     The 

water  of  the  burette  should  be  saturated  with  gas  similar  to  that 
which  is  to  be  analyzed.  The  gas  is  taken  into  the  burette 
through  the  end  of  the  capillary  projecting  out  of  the  left  hand 
side  of  the  case.  If  the  sample  is  drawn  directly  from  the  smoke 
flue  the  precautions  given  in  Chapter  I  on  Sampling  must  be 
observed.  In  any  case  the  burette  is  filled  with  gas  which  is 
then  wasted  through  the  fourth  side  arm  into  the  outside  air, 
thus  getting  rid  of  the  air  which  was  in  the  capillary  tube  of  the 
instrument.  The  sample  of  gas  is  now  drawn  into  the  burette 
and  'measured  with  the  precautions  given  in  Chapter  I.  In 
addition  to  the  gas  which  is  in  the  burette  there  is  a  volume  of 
about  1  c.c.  in  the  capillary  tube  which  is  entirely  neglected. 
The  gas  is  passed  into  the  caustic  pipette  and  CC>2  determined 


FIG.  16. — Orsat  apparatus. 
Moyer  modification. 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS  65 

as  described  in  §  1  of  Chapter  III,  then  into  the  second  pipette 
filled  with  pyrogallate  for  oxygen  (§  4  of  Chapter  III),  then 
into  the  third  pipette  filled  with  cuprous  chloride  for  CO  (§  6  of 
Chapter  III). 

This  apparatus  is  much  used  for  analysis  of  smoke  gases  and 
it  is  sufficiently  accurate  for  this  purpose.  The  errors  which 
arise  from  the  failure  of  the  gas  in  the  capillary  to  come  into 
contact  with  the  reagent  will  hardly  be  more  than  0.1  c.c.  for 
each  of^the  gases.  The  tendency  will  be  for  the  oxygen  to  be 
slightly  high  due  to  some  C02  which  did  not  get  into  the  caustic 
pipette  and  for  the  CO  to  be  high  due  to  oxygen  which  did  not 
get  into  the  pyrogallate  pipette. 

The  Orsat  apparatus  is  not  usually  employed  for  gases  like 
illuminating  gas  where  many  constituents  have  to  be  deter- 
mined, although  other  absorption  pipettes  and  even  explosion 
pipettes  have  sometimes  been  made  a  part  of  the  instrument. 
The  errors  mentioned  above  due  to  the  gas  remaining  in  the 
capillary  increase  with  the  length  of  the  capillary  and  it  becomes 
preferable  to  use  the  burette  with  detachable  pipettes. 

4.  Bunte's  Burette.— Dr.  H.  Bunte1  in  1877  described  his 
burette  which  although  in  the  main  obsolete  still  has  some  uses 
and  is  illustrated  in  Fig.  17.  It  consists  of  a  burette  closed  at 
the  top  by  a  three  way  cock  a  carrying  a  funnel  tube,  and  at  the 
bottom  by  a  cock  b.  The  zero  of  the  burette  is  somewhat  above 
the  lower  cock. 

A  levelling  bottle  such  as  is  used  with  the  ordinary  Hempel 
type  of  gas  burette  is  to  be  connected  to  the  lower  cock.  The 
sample  of  gas  is  drawn  into  the  burette  as  usual  and  its  volume 
may  be  read  as  usual.  The  method  of  reading  the  volume 
prescribed  by  Bunte  is  unusual.  A  sample  of  gas  slightly  larger 
than  100  c.c.  is  to  be  taken  into  the  burette  and  the  volume  com- 
pressed until  it  reads  exactly  100.  Water  is  now  poured  into 
the  funnel  tube  to  the  mark  ra  etched  upon  it  and  cock  a  is  opened 
to  communicate  with  the  funnel  tube  which  is  unstoppered. 
Some  gas  bubbles  through  the  cock  and  the  liquid  above  it  and 
escapes  into  the  air.  The  bore  of  the  cock  is  so  small  that  no 
water  flows  down  and  after  the  bubbling  has  ceased  the  volume 
of  gas  in  the  burette  is  still  100  c.c.  measured  under  the  pressure 

1  Jour,  fiir  GasbeL,  1877,  447. 

5   . 


66 


GAS  AND  FUEL  ANALYSIS 


of  the  atmosphere  plus  the  column  of  water  in  the  funnel  tube. 
The  volume  of  the  gas  is  always  to  be  read  under  these  condi- 
tions. In  order  to  introduce  an  absorbent  such  as  NaOH  into 
the  burette  a  partial  vacuum  is  produced  by  opening  the  lower 
cock  and  lowering  the  levelling  bottle.  The  cock  b  is  then 
closed,  the  levelling  bottle  disconnected  and  the  reagent  in  a 
small  dish  is  placed  below  the  cock  b  so  that  the  tip  of  the  cock 
is  immersed.  On  opening  the  cock  some  of  the  rea- 
gent will  be  sucked  into  the  burette.  The  burette  is 
then  shaken  to  facilitate  absorption,  care  being  taken 
to  hold  it  only  by  the  tips  so  that  the  heat  of  the 
hands  will  not  change  the  temperature  of  the  gas.  To 
read  the  volume  after  absorption  the  funnel  tube  on 
the  top  of  the  burette  is  again  filled  with  water,  and 
the  upper  cock  opened.  Water  flows  into  the  burette 
and  more  water  is  added  to  the  funnel  until  with  the 
upper  cock  still  open  the  water  remains  stationary 
on  the  mark  m.  Conditions  are  now  as  they  were  at 
the  first  reading  and  the  volume  is  again  read.  The 
diminution  in  volume  if  NaOH  was  the  reagent,  is  as 
usual  reported  as  CO2. 

Oxygen  is  determined  by  alkaline  pyrogallate  (§4 
of  Chapter  III).  To  avoid  diluting  the  reagent  the 
dilute  caustic  in  the  burette  is  sucked  out  as  far  as 
possible  and  20  c.c.  of  the  pyrogallate  introduced. 
The  burette  is  shaken  at  intervals  for  five  minutes 
and  then  rinsed  with  fresh  water  introduced  through  the  funnel 
tube,  the  pyrogallate  being  allowed  to  flow  out  of  the  lower 
stopcock.  As  soon  as  the  walls  of  the  burette  are  rinsed  clean 
the  bottom  stopcock  is  closed  and  the  volume  read  as  before 
with  the  top  stopcock  open  and  the  funnel  tube  filled  with  water. 
Carbon  monoxide  is  absorbed  by  acid  cuprous  chloride  as 
usual  (§  6  of  Chapter  III),  but  a  very  considerable  amount  of 
preliminary  manipulation  is  necessary.  The  alkaline  pyrogallate 
must  be  thoroughly  washed  out  by  water  flowing  through  the 
burette  and  then  replaced  by  HC1  sp.  gr.  1.12.  When  this  has 
been  done  the  Cu2Cl2  reagent  may  be  added  and  after  the 
absorption  the  volume  measured  with  the  funnel  tube  filled  with 
dilute  HC1. 


FIG.  17.— 

Bunte  gas 
burette. 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS 


67 


The  only  advantage  which  a  burette  of  this  type  can  claim  is 
its  portability.  Its  manipulation  is  cumbrous,  the  introduction 
of  the  large  volumes  of  wash  water  changes  the  composition  of 
the  gas,  and  the  temperature  of  the  burette,  which  is  usually 
not  jacketed,  is  almost  certain  to  change  unless  very  unusual 
precautions  are  observed  to  keep  it  from  contact  with  the 
hands  of  the  operator  and  to  have  the  temperature  of  the  reagent 
and  wash  water  the  same  as  that  of  the  room  where  the  operation 
is  being  carried  on.  The  Orsat  apparatus  is  preferable  for  almost 
all  purposes. 

5.  Chollar   Tubes.— Mr.    B.    E.    Chollar1   in    1888   modified 

A. 


j 

t 

-*k 

r 

*r= 

-f       1 

===^ 

, 

, 

____" 

t\ 

n 

1                                       <s 

FIG.  18. — Chollar  tubes  for  gas  analysis. 

Cooper's  eudiometer  and  produced  a  very  practical  and  simple 
combination  burette  and  pipette.  In  Fig.  18  at  A  are  seen  three 
of  the  Chollar  tubes  in  a  rack.  The  zero  point  is  the  top  of  the 
bulb  and  the  graduations  start  at  the  bottom  of  the  bulb  and  ex- 
tend down  to  the  bend  in  the  tube.  The  bulbed  portion  may 
1  Proc.  Western  Gas  Association,  1893,  219. 


68  GAS  AND  FUEL  ANALYSIS 

occupy  varying  proportions  of  the  total  volume  and  since  it  is 
not  graduated  a  tube  must  be  chosen  proportioned  properly 
for  the  analysis  to  be  made.  Of  the  three  burettes  shown  at  A, 
that  on  the  right  is  called  a  10  per  cent,  burette  because  the 
graduations  cover  only  10  per  cent,  of  the  total  volume.  The 
middle  burette  is  a  25  per  cent,  burette,  and  the  burette  on  the 
left  is  a  50  per  cent,  burette,  provided  also  with  an  upper  stop- 
cock which  is  convenient,  but  not  necessary  for  all  the  forms. 

It  is  assumed  that  a  plentiful  supply  of  gas  for  analysis  is  avail- 
able and  that  it  is  under  pressure.  A  rubber  tube  is  slipped  into  the 
burette  round  the  bend  and  up  to  the  top  through  which  gas  is 
blown  until  the  air  is  displaced.  It  is  safer  to  fill  the  tube  with 
water  and  displace  this  with  the  gas.  The  rubber  tube  slips 
into  the  burette  more  readily  if  it  is  wet.  When  the  burette  is 
completely  filled  with  gas  it  is  immersed  in  the  cylinder  of  water 
B  far  enough  to  seal  the  outlet  and  the  rubber  tube  is  withdrawn. 
The  burette  is  now  pressed  completely  under  the  water  and  kept 
there  by  the  weighted  cover  C  for  a  few  minutes  until  the  gas 
has  attained  the  temperature  of  the  water  which  should  be  at 
room  temperature.  The  top  of  the  burette  is  then  grasped  by 
the  tip  of  the  fingers  to  avoid  warming  the  gas  and  the  burette 
is  raised  until  the  meniscus  inside  of  the  burette  coincides  with 
the  surface  of  the  water  in  the  glass  cylinder  when  the  gas  vol- 
ume is  read  at  atmospheric  pressure.  In  case  the  volume  of  the 
gas  has  increased  through  expansion  so  that  the  meniscus  is 
below  the  graduations  a  portion  of  the  gas  must  be  removed  by 
closing  the  lower  end  of  the  burette  with  the  thumb  while  it  is 
still  under  water  and  then  by  raising  and  tilting  the  burette 
causing  a  few  bubbles  to  pass  into  the  short  arm  from  which  they 
escape  into  the  air  when  the  thumb  is  removed. 

To  introduce  reagents,  a  portion  of  the  water  is  sucked  from 
the  short  arm  of  the  burette  by  a  pipette  as  shown  at  D.  Suf- 
ficient water  must  of  course  be  left  to  seal  the  burette.  Suf- 
ficient reagent  such  as  caustic  soda  is  then  introduced  to  com- 
pletely fill  the  short  arm  which  is  tightly  closed  by  a  rubber 
stopper  or  the  thumb.  The  burette  is  then  inverted  and  shaken 
until  absorption  is  believed  to  be  complete.  The  gas  which  may 
have  gotten  into  the  short  arm  is  now  worked  back  into  the  body 
of  the  burette  by  turning  the  burette  almost  horizontal  and  the 


APPARATUS  FOR  TECHNICAL  GAS  ANALYSIS  69 

burette  is  again  immersed  in  the  large  cylinder.  The  rubber 
stopper  is  removed  after  the  outlet  is  sealed  with  water,  water 
enters  to  replace  the  gas  absorbed  and  the  volume  of  the  gas  is 
read  as  at  first. 

The  usual  reagents  for  carbon  dioxide,  unsaturated  hydro- 
carbons, oxygen  and  carbon  monoxide  may  be  used.  A  solution 
of  arsenious  oxide  is  recommended  for  hydrogen  sulphide. 

To  wash  out  one  reagent  before  adding  another  the  burette 
is  placed  on  the  stand  shown  at  E  in  Fig.  18  with  its  open  arm 
pointing  down  in  a  beaker  of  water.  The  reagent  being  heavier 
than  water  tends  to  flow  out.  The  washing  may  be  accelerated 
by  passing  water  into  the  burette  through  a  rubber  tube.  The 
instrument  is  very  readily  portable  and  after  a  little  experience 
results  of  considerable  accuracy  may  be  rapidly  obtained. 


CHAPTER  VI 

EXACT  GAS  ANALYSIS 

1.  Historical. — Lavoisier  in  his  Traite*  Elementaire  de  Chemie 
published  in  1789  devoted  Chapter  II  of  Book  III  to  Gasometry 
or  "The  Measurement  of  Weight  and  Volume  of  Gaseous  Sub- 
stances." He  described  eudiometers,  a  gasometer  of  the  bell 
jar  type,  and  methods  of  separation  of  certain  gases  by  absorp- 
tion and  explosion  as  well  as  the  mathematical  method  of  making 
correction  for  temperature  and  pressure. 

Bunsen  and  Playfair1  in  a  paper  "On  the  Gases  Evolved  from 
Iron  Furnaces"  presented  in  1845  what  was  perhaps  the  first 
serious  attempt  to  develop  methods  of  gas  analysis  for  technical 
investigation.  The  methods  published  in  this  paper  formed  the 
basis  of  Bunsen's  classic  book  "  Gasometrische  Methoden" 
published  in  1857.  Bunsen  used  a  graduated  cylindrical  eudi- 
ometer inverted  over  a  trough  of  mercury  both  for  measuring 
the  volume  of  the  gas  and  for  carrying  out  analysis  by  absorp- 
tion and  explosion.  It  was  necessary  to  determine  the  tempera- 
ture and  pressure  of  the  gas  when  each  reading  of  volume  was 
made  and  to  make  arithmetical  corrections  to  bring  the  volume 
to  standard  conditions.  It  was  possible  to  work  accurately 
with  his  apparatus  but  it  has  been  replaced  by  simpler  forms 
which  allow  more  rapid  work. 

Regnault  and  Reiset2  in  a  paper  on  the  respiration  of  animals 
developed  a  eudiometer  which  was  capable  of  accurate  work 
but  was  very  cumbrous. 

Doyere  in  18483  exhibited  before  the  French  Academy  of 
Sciences  apparatus  for  gas  exact  analysis  and  two  years  later4 
presented  details  of  the  remarkably  complete  and  ingenious 
apparatus  which  he  had  devised.  He  used  a  separate  pipette 

1  British  Ass.  for  Advancement  of  Science,  1845,  142. 

2  Ann.  de  Chim.  et  de  Phys.  (3),  26,  299  (1849). 

3  Comptes  rendus  de  V Academic  de  Science,  Feb.,  1848. 
*Annales  de  Chimie,  3  Series,  28,  5,  (1850). 

70 


EXACT  GAS  ANALYSIS  71 

for  each  reagent,  measured  his  gases  saturated  with  moisture 
instead  of  dry,  and  by  means  of  a  mechanical  compensator 
avoided  all  corrections  for  change  in  gas  volume  due  to  tempera- 
ture and  pressure.  He  absorbed  carbon  dioxide  by  caustic 
potash  and  estimated  oxygen  by  explosion  or  by  absorption  with 
ammoniacal  cuprous  chloride,  two  pipettes  being  used  in  series 
followed  by  a  third  containing  dilute  sulphuric  acid.  He  also 
studied  the  estimation  of  hydrogen  by  explosion. 

W.  Hempel  in  the  second  edition  of  his  Gas  Analysis  (1889) 
described  a  modification  of  Doyere's  method  in  which  he  measured 
the  gas  volume  in  a  bulb,  varying  the  pressure  of  the  gas  at  each 
reading  so  that  its  volume  always  filled  the  bulb  to  a  definite 
mark.  The  pressure  under  which  the  gas  stood  was  then  meas- 
ured and  correction  mathematically  made  to  find  the  volume 
under  standard  conditions. 

2.  General    Methods. — These    earlier    processes    with    their 
complications  were  necessitated  by  the  imperfections  of  apparatus, 
especially  stopcocks  which  could  not  be  relied  on  to  be  gas- 
tight.     With  the  development  of  reliable  stopcocks   came  the 
development  of  apparatus  so  that  now  there  is  little  need  to  use 
any  of  these  older  processes.     The  methods  of  exact  gas  analysis 
are  now  in  general  the  same  as  those  employed  in  technical 
analysis  but  with  greater  attention  paid  to  the  elimination  of 
minor  erroTs.     The  gas  burette  is  graduated  more  accurately 
and  an  attempt  is  made  to  read  to  hundredths  of  a  cubic  centi- 
meter instead  of  tenths.     Correction  is  made  either  arithmetically 
or  mechanically  for  variations  in  temperature  and  pressure  of 
the  gas  during  analysis.     Mercury  is  used  instead  of  water  as 
the  confining  liquid  in  the  burette  and  errors  due  to  diffusion 
in  the  pipette  are  prevented.     Special  methods  are  sometimes 
introduced  for  the  estimation  of  minute  constituents  of  the 
gas. 

3.  Corrections   for   Temperature   and   Pressure. — According 
to  the  law  of  Boyle  the  volume  of  any  gas  varies  inversely  as  the 
pressure  and  according  to  the  law  of  Gay  Lussac  all  gases  expand 
under  constant  pressure  by  the  same  amount — about  1/273  of 
their  volume — when  heated  from  0°  C.  to  1°  C.,  and  the  same  for 
each  succeeding  degree.     The  volume  of  a  gas  is  almost  univer- 
sally expressed  in  scientific  work  as  that  which  it  would  occupy 


72  GAS  AND  FUEL  ANALYSIS 

if  completely  dry  and  at  a  temperature  of  0°  C.,  and  a  pressure 
of  760  mm.  of  mercury.  For  technical  purposes  the  gas  is  fre- 
quently calculated  to  the  volume  which  it  would  have  at  60°  F. 
and  30  in.  of  mercury  pressure  when  saturated  with  water.  The 
formulse  for  this  calculation  are  given  in  §  4  of  Chapter  VII  on 
the  Heating  Value  of  Gas. 

The  formula  for  the  reduction  of  the  volume  of  a  dry  gas  to 
0°  and  760  mm.  dry  follows  from  the  laws  stated. 

Vp 


v  __    __  ^ 

"  OI  Vo~ 


(l-.00367t)760 


If  the  gas  as  measured  was  saturated  with  moisture  at  say 
60°  F.  and  it  should  actually  be  chilled  to  0°  C.  most  but  not  all 
of  the  water  would  be  condensed.  It  is  usual  in  calculations 
to  assume  either  that  the  gas  becomes  completely  dried  which 
is  the  usual  assumption  or  that  the  water  all  remains  in  the 
vapor  state  which  is  less  frequently  assumed.  The  formula 
given  above  will  be  the  one  used  in  the  latter  case  where  the 
water  vapor  is  assumed  to  obey  the  gas  laws  without  condensing, 
just  as  nitrogen  or  hydrogen  would. 

If  the  gas  is  to  be  reduced  to  standard  conditions,  dry,  the 
volume  of  the  water  vapor  must  be  deducted.  Since  the 
assumption  is  that  the  gas  is  saturated  with  moisture  at  the 
temperature  "t"  the  proportion  of  moisture  will  be  a  constant 
which  may  be  expressed  either  in  terms  of  volume  or  more 
conveniently  in  terms  of  barometric  pressure.  Table  I  in  the 
Appendix  gives  the  vapor  pressure  of  water,  "a,"  for  each  1°  C. 
within  the  limits  usually  required.  The  formula  for  reduction 
of  the  volume  of  a  gas  read  when  saturated  with  moisture,  to 
its  volume  when  dry  at  0°  C.  and  760  mm.  is  therefore  as  follows: 

V(p-a) 
(l-.00367t)760 

If  the  readings  are  in  the  Fahrenheit  scale  and  in  inches  of 
barometric  pressure  the  formula  becomes 

yi    v<p-a> 


EXACT  GAS  ANALYSIS 


73 


4.  Description  of  Gas  Burettes. — The  burette  for  technical 
analysis  does  not  allow  an  accuracy  greater  than  0.1  c.c.  and  the 
probable  error  is  more  nearly  0.2  c.c.  The  errors  are  in  part 
due  to  the  coarse  graduations  of  the  cylindrical  burette  tube 
and  in  part  to  liability  to  change  in  the  temperature  and  pressure 
under  which  the  gas  volume  is  read.  A  device  for  automatically 
correcting  for  change  in  tempera- 
ture and  barometric  pressure  was 
devised  by  Petterson1  in  an  ap- 


A. 


...:- 


Calibration 
Mar, 


Rubb  ?r 
Com  cotton 


c. 


paratus  for  the  analysis  of  air. 
This  was  quickly  adapted  by 
Hempel  to  his  gas  burette  and 
as  used  by  him  consisted  of  a 
closed  tube  connected  to  one  arm 
of  a  manometer  whose  other  end 
connected  with  one  tip  of  a  three- 
way  cock  at  the  top  of  the  bur- 
ette. The  volume  of  the  gas 
instead  of  being  read  at  a  change- 
able atmospheric  pressure  was  to 
be  read  at  the  unchanging  pres- 
sure in  the  closed  compensating 
tube.  The  modification  of  this 
type  of  apparatus  developed  by 
the  author2  is  shown  in  Fig.  19. 
The  burette  has  a  specially 
bored  stopcock  as  shown  in  the 
sketch  which  allows  communica- 
tion to  be  established  through  the 
stopcock  between  the  burette  and 
the  compensating  tube.  The 

latter  consists  of  a  U  tube  manometer  shown  in  A  of  Fig.  19 
connected  to  the  burette  by  a  single  rubber  connection  at  a, 
placed  so  that  gas  never  comes  in  contact  with  the  rubber  and 
there  can  be  no  possibility  of  leakage — a  fault  of  the  Hempel  type 
of  apparatus.  The  other  end  of  the  U  tube  bends  down  and 
terminates  in  a  tube  about  the  same  diameter  as  the  burette  and 

lZeit.  anal.  Chem.,  25,467  (1886). 
2/<mr.  Am.  Chem.  Soc.,  22,  343  (1900). 


Tr 


FIG.  19. — Details  of  gas  burette 
with  automatic  compensator  for 
temperature  and  pressure. 


74  GAS  AND  FUEL  ANALYSIS 

sealed  at  the  bottom.  At  the  top  of  the  U  is  a  capillary  tip  which 
in  practice  is  fused  shut  as  explained  later. 

In  mounting  the  burette  which  is  assumed  to  be  clean  and 
entirely  taken  apart  the  manometer  is  connected  to  the  burette 
at  a  by  a  piece  of  good  black  rubber  tubing  wired  in  place,  and 
the  large  rubber  stopper  at  the  lower  end  of  the  burette  is  pushed 
up  until  it  rests  snugly  against  the  bottom  of  the  comparison 
tube  and  presses  the  glass  parts  at  a  firmly  together  within  the 
rubber  tube.  The  glass  water  jacket  tube  is  then  slipped  over 
the  top  of  the  burette  and  onto  the  lower  rubber  stopper  and  the 
upper  split  cork  fitted  into  place.  The  burette  is  then  placed 
in  a  stand  such  as  is  shown  in  Fig.  21 .  The  levelling  bottle  is  also 
connected  to  the  burette  as  in  technical  analysis  with  the  added 
precaution  of  wiring  the  rubber  stopper  into  the  burette  so  that  it 
may  not  be  blown  out  through  the  weight  of  the  mercury  column. 
The  process  of  wiring  in  a  rubber  stopper  is  simple  but  since  begin- 
ners are  sometimes  at  a  loss  to  accomplish  it  the  following  descrip- 
tion is  given.  A  piece  of  rubber  tubing  is  first  slipped  over  the 
bottom  of  the  burette  to  give  a  soft  surface  for  the  wire  to  grip. 
A  piece  of  copper  wire  about  18  gage  is  annealed  by  passing 
several  times  through  the  flame  of  a  Bunsen  burner  and  a  piece 
about  4  in.  long  is  twisted  in  the  middle  of  one  about  8  in.  long 
to  form  a  T.  The  longer  piece  is  then  bent  around  the  burette 
and  twisted  till  it  fits  snugly.  Its  two  ends  are  now  brought 
over  the  rubber  stopper  and  twisted  with  the  free  end  of  the  4-in. 
piece  of  wire  until  the  cork  is  firmly  pressed  in. 

To  prepare  the  comparison  tube  for  use,  a  few  drops  of  water 
are  to  be  brought  into  its  lower  portion  to  saturate  the  air  it 
contains,  the  manometer  is  to  be  filled  with  mercury  and  the 
capillary  tip  is  to  be  fused  shut.  The  two  first  operations  can 
be  conveniently  accomplished  in  one  operation.  The  burette 
is  filled  with  mercury  on  whose  surface  are  a  few  drops  of  water. 
By  turning  the  stopcock  to  the  position  shown  at  D  of  Fig.  19, 
the  water  with  the  mercury  following  it  may  be  passed  through 
the  stopcock  and  the  U  tube  and  over  into  the  comparison  tube. 
The  progress  of  the  mercury  is  to  be  arrested  when  the  water 
has  trickled  down  the  comparison  tube  and  the  mercury  is  to  be 
drawn  back  until  there  is  just  enough  left  in  the  U  tube  to  fill  it 
approximately  to  the  calibration  mark  when  there  is  atmospheric 


EXACT  GAS  ANALYSIS  75 

pressure  on  both  limbs  of  the  U  as  shown  in  Fig.  19  at  A.  This 
may  be  readily  accomplished  after  one  or  two  trials.  The  cap- 
illary tip  of  the  comparison  tube  is  now  to  be  sealed  with  a  blow 
pipe  and  the  burette  is  ready  for  use. 

This  burette  has  the  advantage  over  the  usual  technical  type 
that  its  readings  are  unaffected  by  variations  in  external  tempera- 
ture and  pressure,  but  the  volumes  themselves  cannot  be  read 
more  accurately  than  with  the  technical  type  unless  a  reading 
telescope  is  employed.  Even  with  this  aid  to  the  eye  the  results 
are  not  always  certain  for  the  presence  of  a  few  drops  of  water  on 
the  mercury  alters  the  shape  and  boundaries  of  the  meniscus. 

5.  The  Bulbed  Gas  Burette  for  Exact  Analysis.— The  idea  of 
converting  the  burette  into  a  string  of  bulbs  connected  to  a  side 
arm  burette  apparently  originategl  with  Bleier.1 

The  author  has  utilized  this  suggestion  in  the  design  of  the 
burette  shown  schematically  in  Fig.  20,  and  in  perspective  in 
Fig.  21;  it  consists  of  a  burette  with  stopcock  and  manometer 
as  already  described.  The  main  body  of  the  burette  contains 
twelve  bulbs,  each  of  a  capacity  approximating  12  c.c.  A  line  is 
etched  on  each  constriction  and  the  capacity  of  the  bulb  between 
these  marks  is  determined.  Starting  from  the  capillary  above 
the  top  bulb  a  side  arm  springs,  terminating  in  a  small  burette 
with  total  capacity  of  15  c.c.  and  graduated  in  0.1  c.c.  Both 
these  burette  tubes  connect  at  the  bottom  by  means  of  heavy 
rubber  tubes  and  a  Y  with  a  stopcock  on  each  arm,  to  a  common 
levelling  bottle.  A  screw  clamp  on  each  rubber  tube  serves  for 
the  exact  adjustment  of  the  mercury.  To  measure  a  gas,  the 
stopcock  is  placed  in  position  shown  at  C  of  Fig.  19  and  the 
mercury  in  the  bulbed  tube  brought  to  the  mark  in  one  of  the 
constricted  portions  by  opening  the  proper  stopcock  on  the  Y 
and  raising  or  lowering  the  levelling  bottle.  When  adjusted, 
the  mercury  is  held  in  its  proper  position  by  closing  the  stopcock 
on  the  Y.  The  stopcock  leading  to  the  small  burette  tube  is 
then  opened  and  the  gas  brought  to  approximately  atmospheric 
pressure  by  proper  change  in  the  mercury  level.  The  three-way 
stopcock  at  the  top  of  the  burette  tube  being  now  turned  to 
position  shown  at  D  in  Fig.  19,  the  burette  is  brought  into 
connection  with  the  manometer,  which  is  properly  set  by  further 

lBer.  d.  Chem.  Ges.,  31,  1,  238. 


76 


GAS  AND  FUEL  ANALYSIS 


changing  the  level  of  the  mercury  in  the  small  burette.  The 
final  adjustment  in  both  burettes  is  made  by  the  screw  clamps 
on  the  rubber  tubes. 

When  the  gas  burette  is  used  in  the  manner  indicated  the  gas 
volume  is  read  under  conditions  which  are  constant  but  not 
necessarily  known.  It  is  not  usually  necessary  in  gas  analysis 


•Rubber 
Connection 


FIG.  20. — Details  of 
bulbed  gas  burette  for 
exact  gas  analysis. 


FIG.  21. — Burette  for  exact  gas  analysis. 


to  know  the  absolute  value  of  a  gas  but  it  may  be  obtained  if  the 
temperature  and  barometric  pressure  are  noted  at  the  time  the 
tip  of  the  manometer  tube  is  sealed.  The  volume  of  the  gas  is  to 
be  read  when  the  level  of  the  mercury  in  the  two  arms  of  the  man- 
ometer is  the  same.  The  gas  has  then  the  same  volume  which  it 
would  have  had  at  the  temperature  and  pressure  prevailing 
when  the  manometer  was  sealed.  Correction  to  standard  con- 


EXACT  GAS  ANALYSIS  77 

ditions  may  be  made  mathematically  as  indicated  in  a  preced- 
ing paragraph.  This  procedure  for  reading  the  gas  volume  is 
not  as  accurate  as  the  one  recommended  for  gas  analysis  where 
the  mercury  is  brought  tangent  to  the  rim  of  a  metal  sleeve  but 
it  is  amply  accurate  for  most  purposes. 

6.  Manipulation  of  Gas  Burette  for  Exact  Analysis. — It  is 
necessary  to  discharge  from  the  burette  all  of  the  residual  gas  in- 
cluding that  in  the  manometer  tube.  This  may  be  accomplished 
by  discharging  most  of  the  gas  from  the  burette  into  the  air 
and  then  by  turning  the  stopcock  and  lowering  the  levelling 
bottle,  drawing  into  the  burette  the  gas  from  the  manometer 
until  the  mercury  of  the  U  tube  is  just  at  the  stopcock.  The 
gas  in  the  burette  may  then  be  discharged  into  the  air.  If  there 
is  danger  that  alkali  has  been  introduced  into  the  burette  in  a 
previous  operation  it  is  advisable  to  draw  into  the  burette  a  few 
cubic  centimeters  of  acidulated  water  and  with  it  rinse  down  the 
walls  of  the  entire  burette,  subsequently  expelling  it.  This  also 
makes  certain  that  the  walls  of  the  burette  are  wet  so  that  the 
gas  to  be  subsequently  introduced  will  become  saturated  with 
water. 

The  gas  is  then  introduced  into  the  burette  as  in  technical 
analysis.  If  a  volume  of  approximately  one  hundred  cubic 
centimeters  are  wanted,  nine  bulbs  are  filled  with  gas  at  atmos- 
pheric pressure.  The  stopcock  at  the  top  of  the  burette  is  then 
closed  and  the  gas  compressed  into  eight  bulbs.  Up  to  this 
time  the  side  arm  of  the  burette  has  remained  filled  with  mercury. 
The  stopcock  on  the  Y  is  now  opened  and  part  of  the  gas  trans- 
ferred to  the  side  arm  until  the  whole  is  again  under  atmospheric 
pressure  as  shown  by  the  agreement  of  the  level  of  the  mercury 
in  the  levelling  bottle  held  in  the  hand  of  the  operator,  with  the 
level  of  the  mercury  in  the  side  arm.  The  stopcock  on  the  Y  is 
now  to  be  closed  and  that  at  the  top  of  the  burette  is  to  be  turned 
to  make  communication  with  the  manometer  the  mercury  in 
which  drops  at  once  to  approximately  its  proper  position.  By 
using  the  clamps  on  the  rubber  tubes  as  fine  adjustments  the 
meniscus  in  the  bulbed  tube  is  to  be  brought  tangent  to  the 
mark  between  two  bulbs  and  also  the  meniscus  in  the  manometer 
is  to  be  made  tangent  to  the  metal  sleeve. 

The  volume  of  the  gas  will  be  read  as  x  c.c.  in  the  bulbs  +  y 


78  GAS  AND  FUEL  ANALYSIS 

c.c.  in  side  burette  +  z  c.c.  in  manometer.  As  there  are  these 
three  readings  to  be  made  it  is  necessary  that  each  be  very 
accurate.  Let  us  see  how  accurately  this  may  be  done.  First, 
the  mercury  in  the  bulbed  tube  is  to  be  brought  to  a  specified 
mark  in  a  tube  of  about  5  mm.  internal  diameter.  By  means 
of  the  screw  clamp  this  may  be  done  with  such  accuracy  that  the 
error  is  negligible.  Second,  the  volume  of  gas  in  the  side  tube 
must  be  read.  Each  0.1  c.c.  in  this  tube  occupies  a  space  of  a 
little  over  2.5  mm.  and  it  is  possible  to  interpolate  0.01  c.c.  with 
the  eye  with  an  error  of  less  than  0.02  c.c.  Third,  the  mercury 
in  the  manometer  must  be  brought  to  a  definite  mark  with  such 
exactness  that  the  barometric  pressure,  under  which  the  gas 
volume  is  read,  shall  be  almost  identical  each  time.  A  difference 
of  1  mm.  of  mercury  pressure  changes  the  gas  volume  0.13  per 
cent.,  which  on  a  volume  of  100  c.c.  equals  0.13  c.c.,  an  error  far 
too  large.  It  was  found  impracticable  to  attain  the  required 
accuracy  when  it  was  attempted  to  bring  the  mercury  to  a  mark 
etched  on  the  glass.  The  best  device  was  found  to  be  a  band  of 
thin,  blackened  copper,  wrapped  around  the  tube  and  cemented 
to  the  glass.  It  is  possible  to  bring  the  mercury  tangent  to  the 
lower  surface  of  this  with  great  exactness.  In  working  with 
this  burette  the  author  is  accustomed  to  make  all  readings  in 
duplicate,  readjusting  at  all  points  each  time,  and  to  repeat  if 
the  two  differ  from  each  other  by  more  than  0.01  c.c.  Dupli- 
cates usually  agree  within  this  limit.  The  greatest  difficulty 
found  in  manipulation  is  to  draw  the  liquid  from  the  pipette  over 
exactly  to  the  burette  stopcock  and  stop  it  there.  If  it  gets  into 
the  burette,  a  bubble  lodging  in  one  of  the  capillary  tubes  fre- 
quently damps  the  sensitiveness  of  the  manometer.  If  this 
happens  the  bubble  may  be  shot  out  of  its  lodging  place  by  com- 
pressing the  rubber  tube  above  the  screw  clamp  with  the  fingers. 
Such  a  bubble  may  also  be  carried  into  the  manometer,  where 
it  will  obscure  the  surface  of  the  meniscus.  To  remedy  this  it 
is  well  to  keep  2  or  3  mm.  of  water  on  the  surface  of  the  mercury 
in  the  manometer.  This  allows  a  perfectly  sharp  reading  of  the 
mercury  meniscus  below  the  water-level.  The  manometer 
should  respond  to  a  very  slight  movement  of  the  screw  clamp. 
The  advantages  of  this  burette  may  be  summarized  as  follows : 
It  is  a  compact  burette  which,  without  reading-telescope  or  other 


EXACT  GAS  ANALYSIS  79 

accessories,  allows  the  volume  to  be  read  with  an  error  of  less 
than  0.02  c.c.,  compensates  automatically  for  changes  of  tempera- 
ture and  pressure,  and  avoids  completely  all  errors  due  to  in- 
clusion of  air  or  loss  of  gas  in  making  connections  with  the  absorp- 
tion pipettes.  The  disadvantages  so  far  developed  are  chiefly 
those  inherent  in  all  forms  of  apparatus  which  possess  a  stopcock 
and  rubber  connections.  Both  may  leak;  but  on  the  other  hand 
both  may  be  kept  so  tight  for  limited  periods  of  time  as  to  in- 
troduce no  measurable  error. 

7.  Calibration  of  Burette. — The  burette  must  be  carefully 
calibrated  throughout  its  entire  length.  This  can  best  be  done  by 
weighing  the  mercury  discharged.  One  cubic  centimeter  of  mer- 
cury at  0°  C.  weighs  13.59  grm.  Since  all  that  is  desired  is  a 
relative  calibration  the  mercury  need  not  be  strictly  pure  nor 
need  correction  be  made  for  its  temperature.  Ten  milligrams 
of  mercury  corresponds  to  less  than  one-thousandth  of  a  cubic 
centimeter  so  greater  accuracy  than  this  in  weighing  is  a  waste  of 
time.  Wire  a  stopper  carrying  a  stopcock  into  the  bulbed  tube 
and  fasten  by  a  stiff  rubber  tube  a  stopcock  to  the  side  arm.  It 
is  especially  important  that  the  rubber  tubing  should  not  bulge 
under  the  mercury  pressure  and  to  prevent  this  it  should  be  firmly 
wound  with  wire.  Connect  the  tips  of  these  stopcocks  to  the 
mercury  levelling  bottle  and  through  them  fill  the  burette  with 
mercury  completely  to  the  stopcock.  The  portion  first  calibrated 
is  the  capillary  tube  from  the  bottom  of  the  stopcock  to  the  zero 
of  the  bulbed  tube  and  the  zero  of  the  side  arm.  After  that  each 
bulb  and  each  cubic  centimeter  of  the  side  arm  is  separately 
calibrated.  The  accuracy  of  the  calibration  may  be  checked  by 
the  procedure  of  a  regular  analysis  where  a  volume  of  gas  is  chosen 
such  that  it  for  instance  fills  9  bulbs  and  a  small  portion  of  the  side 
arm.  The  method  of  reading  may  then  be  changed  to  eight  bulbs 
plus  a  considerable  volume  in  the  side  arm  but  if  the  calibration  is 
correct  the  same  volume  should,  of  course,  be  shown.  The  vol- 
ume of  the  small  portion  of  the  manometer  tube  above  the  mer- 
cury may  best  be  determined  by  filling  the  burette  completely 
with  mercury  and  then  drawing  the  air  out  of  the  manometer 
tube  into  the  side  arm  of  the  burette  where  it  may  be  measured 
under  atmospheric  pressure  with  an  error  of  a  few  tenths  of  a  per 


80  GAS  AND  FUEL  ANALYSIS 

cent.     Since  the  total  volume  is  only  a  small  fraction  of  a  cubic 
centimeter  the  method  is  amply  accurate. 

8.  Absorption  Methods  in  Exact  Gas  Analysis — The  same 
reagents  may  in  general  be  used  in  exact  as  in  technical  analysis. 
Care  should  however  be  taken  to  see  that  the  reagent  has  been 
recently  saturated  with  gas  of  a  sort  similar  to  that  which  is  to  be 
analyzed.     In  case  the  reagent  is  one  which  does  not  attack  mer- 
cury the  pipette  is  to  be  filled  with  mercury  which  carries  on  its 
surface  only  a  few  cubic  centimeters  of  the  reagent.     If  pipettes 
of  the  ordinary  type  are  filled  with  mercury  the  mercury  rising 
in  the  second  bulb  places  the  gas  under  considerable  pressure  and 
greatly  increases  the  danger  of  leakage  at  the  rubber  connections. 
An  explosion  pipette  may  with  advantage  be  used  as  an  absorption 
pipette  under  these  circumstances  since  its  stopcock  and  levelling 
bottle  allow  a  regulation  of  the  pressure  within  the  pipette. 
Where  the  greatest  accuracy  is  not  required  it  is  sufficient  to  lessen 
the  errors  due  to  diffusion  by  introducing  a  few  cubic  centimeters 
of  mercury  to  form  a  seal  in  the  ordinary  form  of  pipette.     In 
the  case  of  solutions  like  cuprous  chloride  where  mercury  cannot 
be  used  reliance  must  be  placed  on  the  complete  saturation  of  the 
reagent.     Where  gases  are  readily  soluble  errors  due  to  diffusion 
mount  up  rapidly.     For  instance :  A  sample  of  74  c.c.  of  acetylene 
gas  when  passed  into  an  ordinary  KOH  pipette  as  used  in  tech- 
nical gas  analysis  decreased  to  63.9  after  quietly  standing  for  three 
minutes,  to  58.0  after  a  second  contact,  and  to  29.0  c.c.  after  three 
minutes  shaking  with  the  same  reagent.     After  two  more  similar 
periods  the  residue  left  in  the  burette  was  only  5.2  c.c.     A  second 
sample  of  gas  behaved  similarly,  and  by  connecting  a  burette 
with  the  second  bulb  of  the  pipette  the  acetylene  diffusing  through 
was  recovered  quantitatively. 

9.  Carbon  Dioxide. — Carbon  dioxide  is  usually  estimated  by 
absorption  'in  caustic  soda  as  in  technical  analysis.     If  other 
acid  gases  such  as  H2S,  S02,  or  HC1  are  present  they  may  be  re- 
moved by  first  shaking  the  gas  in  a  pipette  containing  KMn04 
very  faintly   acidified  with    H2SO4.     An  increase    in   volume 
after    this   operation   would    indicate   that   oxygen   had   been 
evolved  during  the  process.     If  direct  evidence  of  the  presence  of 
CO2  is  desired  a  clear  solution  of  Ba(OH)2  should  be  used  instead 
of  NaOH  in  the  pipette  for  C02  absorption.     The  formation  of  a 


EXACT  GAS  ANALYSIS  81 

white  precipitate  completely  soluble  in  HC1  will  show  the  presence 
of  carbonates. 

10.  Unsaturated  Hydrocarbons. — Unsaturated  hydrocarbons 
as  a  class  are  estimated  as  in  technical  gas  analysis  by  absorption 
with  fuming  sulphuric  acid  or  bromine  water.  It  is  difficult  to 
prevent  the  errors  due  to  diffusion  mentioned  in  §  8  since  both 
reagents  attack  mercury.  Where  it  is  desirable  to  eliminate  the 
error  as  far  as  possible  a  stopcock  may  be  placed  in  the  line  be- 
tween the  two  bulbs  of  the  pipette  which  can  be  closed  after  the 
gas  has  been  passed  into  the  pipette  while  absorption  is  taking  place. 

A  separation  of  the  constituent  Unsaturated  hydrocarbons  is 
rarely  carried  out.  It  is  best  accomplished  by  bubbling  a  known 
volume  of  the  gas  through  bromine  and  fractionating  the  resulting 
bromides.  The  results  are  at  best  unsatisfactory.  Ernshaw1 
has  shown  that  it  is  possible  to  calculate  the  average  composition 
of  the  illuminants  from  data  obtained  by  exploding  a  sample  of 
the  gas  which  still  contains  the  olefmes  and  deducting  from  the 
observed  contraction  and  carbon  dioxide  the  amounts  due  to 
hydrogen,  carbon  monoxide  and  the  paraffines.  The  method  de- 
mands very  accurate  work. 

Acetylene  may  be  absorbed  in  a  faintly  ammoniacal  solution  of 
silver  or  copper  salts.  The  precipitated  acetylides  are  explosive 
when  dried  and  care  should  be  taken  in  handling  them.  The 
ammonia  vapors  are  to  be  removed  from  the  gas  by  shaking  with 
dilute  acid  before  the  volume  is  measured.  Water  dissolves  more 
than  its  own  volume  of  acetylene,  so  great  care  must  be  exercised 
to  saturate  the  water  of  containing  vessels  before  the  gas  to  be 
analyzed  is  brought  into  them.  Also  gas  from  which  large  per- 
centages of  acetylene  have  been  removed  must  not  be  returned  to 
vessels  containing  much  water  with  which  it  had  previously  been 
in  equilibrium  since  the  water  will  give  back  to  the  gas  material 
amounts  of  acetylene. 

Phosphorus  forms  a  delicate  reagent  for  qualitative  detection 
of  traces  of  Unsaturated  hydrocarbons.  If  when  the  gas  in 
question  is  brought  in  contact  with  phosphorus  under  the  con- 
ditions prescribed  for  the  estimation  of  oxygen,  white  fumes 
form,  it  is  certain  evidence  of  the  absence  of  more  than  minute 
traces  of  unsaturated  hydrocarbons.  If  on  the  other  hand  the 

1  Jour.  Franklin  InsL,  146,  161  (1898). 

6 


82  GAS  AND  FUEL  ANALYSIS 

fumes  fail  to  appear,  even  after  the  addition  of  air  it  is  not 
absolutely  certain  that  the  inhibiting  catalyzer  is  an  unsaturated 
hydrocarbon  for  ether,  chloroform  and  a  number  of  other  sub- 
stances behave  similarly. 

11.  Oxygen. — The  estimation    of  oxygen  by  phosphorus  as 
in  technical  analysis  admits  of  little  improvement  in  simplicity 
or  accuracy.     Alkaline  pyrogallate  may  be  used  where  it  is  not 
possible  to  remove  the  inhibiting  catalyzers  which  prevent  the 
use  of  phosphorus. 

12.  Carbon  Monoxide. — It  was  stated  in  Chapter  II  that 
the  methods  for  estimation  of  carbon  monoxide  were  unsatis- 
factory.    They    are    more    unsatisfactory    for    exact    than    for 
technical  analysis.     The  absorption  by  cuprous  chloride  given 
in  technical  methods  is  hardly  to  be  considered  as  an  accurate 
method.     The  change  in  the  absorption  spectrum  of  blood  after 
treatment  with  carbon  monoxide  may  be  made  an  accurate 
qualitative  test  for  carbon  monoxide  but  does  not  lend  itself 
readily  to  quantitative  purposes. 

The  method  usually  employed  is  to  oxidize  the  carbon  monoxide, 
after  having  made  certain  that  all  other  compounds  which 
would  be  affected  by  the  oxidizing  agent  have  been  removed. 

Iodine  pentoxide  is  the  most  commonly  employed  oxidizing 
agent,  the  reaction  being : 

I205+5CO  =  I2+5CO2 

The  especial  value  of  this  reaction  lies  hi  the  ease  with  which 
the  iodine  formed  may  be  estimated,  it  being  the  iodine  and  not 
the  carbon  dioxide  which  is  used  to  measure  the  amount  of 
carbon  monoxide.  The  details  here  given  are  essentially  those 
of  Kinnicutt  and  Sanford,1  who  used  substantially  the  method 
of  Nicloux.  The  gas  is  first  purified  by  being  bubbled  slowly 
through  concentrated  sulphuric  acid  and  then  passed  through  a 
tube  containing  lumps  of  caustic  soda.  This  treatment  removes 
unsaturated  hydrocarbons,  hydrogen  sulphide,  sulphur  dioxide 
and  similar  reducing  gases.  The  purified  gas  is  then  passed 
through  iodine  pentoxide  contained  in  a  U  tube  immersed  in  an 
oil  bath  at  150°  C.  Following  the  U  tube  comes  another  ab- 
sorption tube  containing  about  0.5  g  potassium  iodide  dissolved 
1  Jour.  Am.  Chem.  Soc.,  22,  15  (1900), 


EXACT  GAS  ANALYSIS  83 

in  10  c.c.  of  water.  If  a  liter  of  gas  is  used  as  small  an  amount 
as  0.025  c.c.  of  carbon  monoxide  may  be  detected.  The  method 
is  ordinarily  only  used  for  the  detection  of  minute  amounts  of 
carbon  monoxide  and  it  is  not  suitable  for  large  amounts. 
The  absence  of  any  liberated  iodine  may  be  considered  a  positive 
proof  of  the  absence  of  carbon  monoxide.  The  liberation  of 
iodine  is  however  only  a  proof  that  some  reducing  substance 
was  present,  which  can  only  with  certainty  be  claimed  as  carbon 
monoxide  after  careful  blank  tests  have  shown  that  the  purifying 
train  is  adequate  to  remove  all  other  reducing  substances  and 
that  the  iodine  pentoxide  does  not  yield  iodine  except  in  the 
presence  of  such  a  reducing  substance. 

Gill  and  Bartlett1  tested  this  method  on  illuminating  gas 
and  report  results  about  nine  per  cent.  high.  They  report 
accurate  results  when  mixtures  of  carbon  monoxide  and  air  are 
used. 

13.  Hydrogen. — Hydrogen  may  be  directly  absorbed  in 
metallic  palladium  but  is  almost  always  oxidized.  The  gas 
should  first  be  freed  from  unsaturated  hydrocarbons  and  other 
reducing  gases  as  well  as  oxygen,  so  that  it  contains  only  hydrogen, 
saturated  hydrocarbons  and  nitrogen.  There  is  then  a  choice 
of  methods — one  class  oxidizing  the  hydrogen  without  affecting 
the  hydrocarbons,  and  the  other  simultaneously  oxidizing  both 
hydrogen  and  hydrocarbons. 

There  are  several  methods  for  fractional  oxidation  of  hydrogen 
which  are  reliable.  The  errors  which  attend  the  method  of 
simultaneous  oxidation  of  hydrogen  and  methane  have  been 
briefly  discussed  in  ChapteT  IV.  The  important  systematic 
error  in  explosions  and  flame  combustions  is  due  to  the  oxidation 
of  nitrogen.  The  formation  of  oxides  of  nitrogen  increases  with 
higher  temperatures.  The  most  favorable  mixture  for  their 
formation  is  one  in  which  there  are  equal  volumes  of  oxygen  and 
nitrogen.  The  errors  are  therefore  minimised  by  keeping  the 
temperature  of  combustion  low  and  by  making  the  diluting  gas 
as  nearly  pure  oxygen  as  possible.  It  is  not  possible  to  give  an 
absolute  statement  of  the  magnitude  of  the  error  introduced 
for  it  will  vary  with  each  difference  in  the  form  of  the  explosion 
vessel  and  in  the  violence  of  the  explosion.  The  following 

1  Jour.  Ind.  and  Eng.  Chem.,  2,  9  (1910). 


84 


GAS  AND  FUEL  ANALYSIS 


series  of  measurements  by  the  author1  will  indicate  the  magnitude 
of  the  error  and  also  the  accuracy  of  the  burette  for  exact  gas 
analysis  described  in  this  chapter. 

EXPLOSION  OF  PURE  HYDROGEN 


Hydrogen, 
c.c. 

Air, 
c.c. 

Contraction 
after  explo- 
sion, c.c. 

Calculated 
per  cent, 
hydrogen 

Contraction 
over  potas- 
sium hydrox- 
ide, c.c. 

Explo- 
sive 
ratio 

11.35 

84.80 

16.90 

99.26 

0.00 

4.64 

12.11 

85.57 

18.08 

99.53 

0.00 

4.37 

14.19 

84.27 

21.27 

99.92 

0.00 

3.62 

16.77 

85.77 

25.13 

99.90 

0.01 

3.06 

16.54 

82.64 

24.76 

99.80 

0.01 

3.00 

18.19 

83.22 

27.29 

100.01 

0.01 

2.71 

21.10 

83.28 

31.74 

100.28 

0.00 

2.29 

27.04 

83.86 

40.80 

100.59 

0.11 

1.73 

The  hydrogen  was  prepared  by  the  action  of  caustic  potash 
on  aluminium  so  as  to  be  free  from  hydrocarbons.  It  will  be 
noted  that  in  this  series  air  was  used  to  supply  the  oxygen  and  as 
the  diluent.  A  variation  of  1.3  per  cent,  in  the  purity  of  hy- 
drogen due  solely  to  errors  inherent  in  the  explosion  process  make 
it  evident  that  the  method  can  hardly  be  called  an  accurate  one. 

The  errors  attendant  upon  the  flame  combustion  method  of 
Dennis  and  Hopkins  described  in  §  9  of  Chapter  IV  are  illustrated 
in  the  following  series. 

COMPARISON   OF   EXPLOSION   AND   COMBUSTION   METHODS 
ON  HYDROGEN 

Explosions  with  Air 


Sample 
hydrogen 
c.c. 

Air 
c.c. 

Contraction 
after  explo- 
sion, c.c. 

Contraction 
over  potassium 
hydroxide,  c.c. 

Hydrogen 
per  cent. 

Explo- 
sive 
ratio 

15.32 
18.15 

85.34 
82.39 

22.71 
26.93 

0.04 
0.06 

98.82 
98.91 

3.43 
2.73 

Explosions  with  Oxygen 


1  Oxygen  | 

1 

! 

14 
16 
20 

82 

48 
'58 

93.51 
82.18 
80.09 

22 
24 
30 

04 
51 
60 

0 
0 
0 

02 
02 
03 

99 
99 
99 

14 
15 
12 

3 
3 
2 

91 
02 
29 

1  Jour.  Am.  Chem.  Soc.,  23,  476  (1901). 


EXACT  GAS  ANALYSIS 
Combustions  by  the  Dennis  and  Hopkins  Method 


85 


Hydrogen 
c.c. 

Oxygen 
c.c. 

Air 
c.c. 

Contraction 
after  explo- 
sion, c.c. 

Contraction 
over  potassium 
hydroxide,  c.c. 

Hydro- 
gen 
percent. 

Oxygen 
in  excess 

91.29 

58.48 
89.31 

51.65 
53.39 
40.77 

54.55 
50.14 
50.21 

136.72 
87.43 
133.57 

0.04 
0.10 
0.07 

99.84 
99.66 
99.70 

13.72 
40.89 
3.73 

The  values  obtained  by  explosion  with  oxygen  are  remarkably 
concordant  and  are  probably  as  accurate  as  we  can  hope  to 
attain.  The  values  obtained  by  explosion  with  air  are  higher 
and  more  irregular.  The  values  of  the  Dennis  and  Hopkins 
method  are  also  high  and  involve  an  error  of  about  0.6  per  cent. 

14.  Methane. — There  are  no  absorption  methods  for  methane 
which  are  acceptable.  It  is  estimated  by  oxidation  to  CC>2 
and  H2O  with  measurement  of  the  change  in  volume  after 
oxidation  and  after  absorption  of  the  C02-  The  general  methods 
are  given  in  §  7  to  1 1  of  Chapter  IV.  There  is  greater  liability  of 
error  in  the  explosion  process  through  formation  of  oxides  of 
nitrogen  than  is  the  case  with  hydrogen,  as  is  illustrated  by  the 
following  series  of  tests  of  methane  made  from  methyl  iodide 
and  the  zinc  copper  couple. 

EXPLOSION  OF  METHANE 


Sample 
methane 
c.c. 

Air 
c.c. 

Contrac- 
tion after 
explosion 

Carbon 
dioxide 
c.c. 

Methane 
per  cent. 

Hydro- 
gen per 
cent. 

Explo- 
sive 
ratio 

Ratio 
contrac- 
tion 

sample 

7.05 
8.93 
9.07 
10.20 

92.07 
104.17 
98.35 
98.22 

13.09 
16.66 
17.10 
19.27 

6.53 
8.31 
8.54 
9.63 

92.62 
93.28 
94.15 
94.41 

0.28 
0.14 
0.14 
0.06 

4.05 
3.53 
3.19 
2.61 

1.85 
1.86 
1.88 
1.89 

In  these  experiments  the  explosive  ratios  all  lie  within  the  limits 
set  by  Bunsen.  Still  there  is  a  variation  of  1.6  per  cent,  in  the 
apparent  percentage  of  methane  as  calculated  by  the  usual 
methods  and  a  corresponding  variation  in  the  amount  of  hydro- 
gen. Similar  experiments  made  with  commercial  oxygen  (96.5 
per  cent,  pure)  as  the  diluting  agent  instead  of  air  showed  errors 
rather  greater  than  when  using  air  in  similar  amount.  The 
greater  error  in  analyzing  methane  as  compared  with  hydrogen 


86  GAS  AND  FUEL  ANALYSIS 

results  almost  certainly  from  the  higher  temperatures  attained 
in  the  explosion  of  methane.  It  is  not  possible  to  dilute  the  gas 
sufficiently  to  avoid  this  danger  without  running  the  risk  of 
incomplete  combustion  of  the  methane.  The  methods  of 
oxidation  of  methane  which  involve  flame  as  in  explosion  or  the 
Dennis  and  Hopkins  method  cannot  be  considered  very  accurate. 
Jaeger's  method  of  analysis  by  combustion  with  copper  oxide 
in  a  combustion  tube  as  described  in  §  11  of  Chapter  IV 
cannot  involve  the  formation  of  material  amounts  of  oxides 
of  nitrogen.  This  method  is  not  so  rapid  or  convenient  as 
the  others  but,  if  care  is  taken  to  carefully  cool  the  gas  includ- 
ing that  remaining  in  the  combustion  tube  to  its  initial  temper- 
ature before  noting  the  change  in  volume,  it  is  believed  to  be  the 
most  accurate  method. 

15.  Nitrogen. — The  method  of  removal  of  all  gases  except 
nitrogen  by  combustion  with  copper  oxide  as  given  in  §  12  of 
Chapter  IV  is  fairly  exact.  The  gases  of  the  argon  group  are 
left  with  the  nitrogen  but  the  separation  of  these  is  not  included 
in  this  work. 


CHAPTER  VII 
HEATING  VALUE  OF  GAS 

1.  Introduction. — The  heating  value  of  gases  may  be  deter- 
mined by  combustion  in  a  bomb  calorimeter  but  the  difficulty 
of  transferring  a  definite  quantity  of  gas  to  the  bomb  prevents 
the  general  adoption  of  such  a  method.     The  standard  type  of 
calorimeter  is  one  in  which  the  gas  is  burned  with  atmospheric 
air  and  the  total  heat  of  the  products  of  combustion  is  as  com- 
pletely as  possible  transferred  to  the  water  of  the  calorimeter.     A 
continuous  flow  calorimeter  is  usually  employed  wherever  a 
sufficient  amount  of  gas  is  available,  but.  the  intermittent  type  is 
also  used.     In  some  other  types  of  calorimeter  the  heat  of  com- 
bustion is  used  to  raise  the  temperature  of  a  piece  of  metal,  or  a 
thermocouple  placed  in  the  flame.     Calorimeters  of  these  latter 
types  give  merely  relative  figures  which  can  only  be  converted 
into  heat  values  after  very  careful  calibration.     They  are  in 
no  sense  standard  instruments  and  are  not  discussed  in  this  book. 
It  is  also  possible  to  calculate  the  heating  value  of  the  gas  from 
its  chemical  composition  with  approximate  accuracy. 

2.  Continuous    Flow    Calorimeters. — The    continuous    flow 
calorimeter  bears  much  resemblance  to  the  type  of  instantaneous 
water  heaters  found  in  bath  rooms.     The  gas  after  passing 
through  a  meter,  is  burned  in  a  Bunsen  burner.     The  products  of 
combustion  give  up  their  heat  to  a  stream  of  cold  water  flowing  in 
a  direction  opposite  to  that  of  the  gases  so  that  the  gases  emerge 
from  the  instrument  cold  and  the  water  emerges  hot. 

The  process  to  be  accurate  requires  the  fulfillment  of  the  follow- 
ing conditions: 

a.  The  gases  must  be  accurately  measured,  be  burned  at  a 
constant  rate,  and  combustion  must  be  complete. 

b.  The  water  must  enter  at  a  constant  rate  and  at  constant 
temperature,  and  be  at  approximately  room  temperature. 

c.  The  heat  of  combustion  must  all  be  transmitted  to  the 

87 


88  GAS  AND  FUEL  ANALYSIS 

water  whose  mass  and  rise  in  temperature  must  be  accurately 
determined. 

The  pioneer  calorimeter  of  this  type  was  that  devised  by  Hugo 
Junkers  in  1893.1  It  is  an  excellent  -and  widely  used  instru- 
ment which  has  in  recent  years  had  several  imitators.  It 
will  be  described  in  detail  after  a  discussion  of  the  general 
principles. 

3.  Wet  Gas  Meters. — The  gas  is  usually  measured  in  a  wet 
meter  which  consists  of  a  horizontal  cylindrical  casing  of  sheet 
metal  enclosing  a  horizontal  drum  and  filled  about  half  full  of 
water.  The  drum  is  divided  with  slant  partitions  into  three  or 
four  compartments,  each  with  its  own  entrance  for  gas  at  the 
back  and  its  exit  at  the  front.  Each  of  these  compartments  con- 
stitutes a  distorted  screw  thread  enlarged  to  a  chamber  in  the 
center.  As  the  inlet  of  one  of  these  compartments  comes  out  of 
the  water  the  pressure  of  the  gas  entering  causes  the  drum  to 
revolve  and  the  compartment  fills  with  gas.  When  the  compart- 
ment is  full  the  inlet  dips  below  the  water  and  seals,  the  outlet 
unseals  and  the  water  entering  the  compartment  drives  out  the 
gas  before  it.  If  there  were  only  one  or  two  compartments  the 
flow  of  gas  could  not  be  continuous,  but  with  three  or  four  com- 
partments in  the  drum,  one  is  always  discharging  and  the  rate  of 
flow  of  gas  is  about  constant. 

It  will  readily  be  seen  that  the  capacity  of  each  compartment 
and  the  time  of  sealing  and  unsealing  the  inlet  and  outlet  will 
be  affected  by  the  height  of  water  in  the  meter  so  that  the  exact 
setting  of  the  water  level  becomes  of  great  importance.  Each 
meter  is  provided  with  a  gage  glass  and  a  pointer  which  can  be 
adjusted  to  indicate  the  proper  water  level.  The  Committee  on 
Calorimetry  of  the  American  Gas  Institute  in  its  1912  report 
states  that  even  with  careful  work  an  error  of  0.3  per  cent,  may 
be  introduced  by  inaccurate  adjustment  of  the  water  level  and 
that  on  passing  100  cubic  feet  of  gas  through  the  meter  an  error  of 
about  equal  magnitude  may  be  introduced  through  evaporation 
of  the  water.  The  meter  must  be  calibrated  frequently  for  accu- 
rate work. 

Although  it  may  be  desirable  to  use  the  imported  Junkers 
calorimeter,  there  is  no  similar  reason  for  using  the  German  meter 

1  Jour,  fur  Gasbel,  36,  81  (1893). 


HEATING  VALUE  OF  GAS  89 

which  reads  in  the  metric  system.  An  American  meter  passing 
0.1  cu.  ft.  per  revolution  is  much  more  convenient. 

The  gas  meter  must  be  calibrated  by  passing  through  it  a 
known  volume  of  gas.  This  known  volume  may  most  accurately 
be  obtained  by  the  use  of  what  is  known  as  a  cubic  foot  bottle  or  a 
smaller  container  of  the  same  type.  Containers  of  this  type 
should  be  rigidly  made  of  glass  or  metal  and  tapered  at  the  top  and 
bottom  to  glass  tubes  of  small  diameter  upon  which  zero  marks  are 
etched.  The  capacity  of  one  of  these  containers  is  determined  by 
the  weight  of  water  which  it  contains.  They  may  be  bought  in 
elaborate  forms  and  with  the  certificate  of  the  Bureau  of  Stan- 
dards. Where  a  standardized  bottle  is  not  available  a  sufficiently 
accurate  substitute  may  be  improvised  from  a  gas  holder  of  the 
type  shown  in  Fig.  24.  This  consists  of  a  cylinder  of  galvan- 
ized iron  coned  and  terminated  with  a  cock  at  both  ends.  If 
this  is  filled  with  water  at  room  temperature  and  weighed,  and 
then  drained  and  weighed,  the  volume  of  the  tank  may  be  cal- 
culated from  the  following  table.  The  volume  thus  obtained 
may  be  considered  constant  within  ordinary  ranges  of  temper- 
ature since  the  coefficient  of  expansion  of  mild  steel  is  only 
0.0000067  per  degree  Fahrenheit. 

The  tank  shown  in  the  illustration  holds  one-third  of  a  cubic 
foot  and  is  weighed  upon  the  balance  shown  in  front  of  it.  If 
larger  tanks  are  used  they  must  be  made  of  heavy  material  so  as 
not  to  change  in  volume  when  filled  with  water. 

WEIGHT  OF  ONE  CUBIC  FOOT  OF  WATER 

50°  F 62.411b. 

60°  F 62.371b. 

70°  F 62.311b. 

80°  F 62.231b. 

90°  F 62.131b. 

In  making  the  test  the  tank  is  to  be  filled  absolutely  full  of 
water  of  almost  room  temperature  and  left  standing  by  the  side 
of  the  meter  in  a  room  of  fairly  constant  temperature  for  several 
hours  to  make  sure  that  all  the  parts  of  the  system  are  at  the 
same  temperature.  The  gas  supply  is  to  be  bubbled  through 
water  in  order  to  be  certain  that  it  is  saturated  with  water  vapor. 


90  GAS  AND  FUEL  ANALYSIS 

If  the  depth  of  water  in  the  saturator  is  so  adjusted  that  no  gas 
bubbles  through  unless  a  very  slight  suction  is  applied,  it  will 
obviate  mathematical  corrections,  because  if  the  static  pressure 
of  the  water  in  the  saturator  is  adjusted  to  counterbalance  the 
pressure  of  the  incoming  gas,  and  the  outlet  of  the  discharge 
from  the  tank  is  set  at  the  level  of  the  lower  cock,  a  direct  com- 
parison of  the  volume  of  gas  registered  by  the  meter  and  the  capac- 
ity of  the  tank  gives  the  calibration  factor  for  the  meter  without 
any  calculation  for  difference  in  pressure.  So  long  as  the  whole 
system  is  at  the  same  temperature  it  is  immaterial  what  the 
temperature  is.  The  upper  cock  of  the  tank  may  now  be  con- 
nected directly  to  the  outlet  of  the  meter.  The  lower  cock  of  the 
tank  should  have  a  rubber  tube  attached  which  drops  down  to 
allow  the  formation  of  a  water  seal  and  rises  again  to  discharge  the 
water  at  the  level  of  the  cock.  If  now  the  lower  cock  on  the  tank 
is  opened  Water  will  flow  out  through  the  rubber  tube  and  an 
equal  volume  of  gas  will  flow  through  the  meter.  When  the  water 
is  all  out  of  the  tank  the  gas  will  be  automatically  stopped  by 
the  water  seal  in  the  rubber  outlet  tube  and  the  whole  system 
will  be  under  atmospheric  pressure,  which  is  a  condition  necessary 
for  accurate  work. 

4.  Corrections  for  Temperature  and  Pressure. — The  volume 
of  the  gas  used  in  a  test  must  be  corrected  for  temperature  and 
pressure.  The  standard  conditions  for  the  United  States  and 
Great  Britain  are  a  temperature  of  60°  F.  and  a  barometric 
pressure  of  30  in.  of  mercury.  The  gas  as  it  comes  from  the  wet 
meter  is  assumed  to  be  saturated  with  water  and  correction  is 
made  for  the  excess  of  water  vapor  over  that  normal  for  60°. 
Tables  giving  the  correction  factors  in  convenient  form  have  been 
issued  by  the  Gas  Referees  of  London.  They  are  derived  accord- 
ing to  the  formula. 

_17.64(h-a) 
460+t 

where  n  =  factor  sought 

h  =  height  of  barometric  column  in  inches  mercury 
a  =  vapor  tension  in  inches  of  mercury  at  temp,  t 
t  =  observed  temp,  of  meter  in  degrees  F. 


HEATING  VALUE  OF  GAS  91 

Although  this  formula  apparently  involves  the  full  correction 
for  vapor  tension  which  would  reduce  the  volume  of  gas  to  a  dry 
basis  at  60°  F.,  there  is  a  further  correction  contained  in  the  figure 
17.64  of  the  formula  which  corrects  the  gas  to  a  basis  of  60°  F. 
when  saturated  with  water.  The  full  formula  is  as  follows  : 


The  first  member  of  the  formula  corrects  the  volume  to  32°  F., 
the  second  to  60°  F.,  the  third  to  dry  gas  under  30  in.  barometric 
pressure,  and  the  fourth  to  gas  saturated  with  moisture  at  60° 
F.  the  0.51  being  the  vapor  pressure  of  water  at  60  °  F.  Table 
III  in  the  Appendix  gives  the  factors  for  each  degree  Fahrenheit 
and  each  0.1  in.  pressure  within  wide  limits. 

5.  Control  of  the  Water.  —  The  water  supply  must  always  be 
sufficient  to  keep  the  overflow  on  the  small  elevated  constant- 
level  tank  in  operation.     If  the  supply  of  water  to  the  tank 
slackens  much  the  rate  of  flow  to  the  calorimeter  will  also  change. 
The  temperature   of  the  water  should  also  be    constant   and 
approximately  that  of  the  room.     In  order  to  insure  a  water 
supply  or  even  temperature  and  pressure  it  is  advisable  to  install 
in  the  calorimeter  room  an  elevated  tank  of  at  least  20  gallons 
capacity  connected  to  the  water  mains  and  provided  with  an  over- 
flow from  which  the  supply  for  the  calorimeter  is  drawn. 

6.  Measurement  of  Temperature.  —  The  temperature  of  the 
inflowing  and  outgoing  water  is  determined  by  thermometers 
which  should  read  to  tenths  of  a  degree.     They  must  be  carefully 
calibrated  throughout  their  length  by  comparison  with  a  stand- 
ard.    It  is  immaterial  whether  they  are  Centigrade  or  Fahrenheit 
thermometers  but  the  Fahrenheit  are  more  convenient,  when  as 
is  customary,  the  results  are  to  be  expressed  in  British  thermal 
units  per  cubic  foot  of  gas.     The  thermometers  are  to  be  carefully 
placed  in  the  calorimeter  so  that  their  bulbs  are  completely  sur- 
rounded by  water  and  are  nowhere  in  contact  with  the  metal  of 
the  calorimeter. 

7.  Measurement   of   Mass   of  Water.  —  The   mass   of  water 
heated  during  an  experiment  may  be  determined  either  by  meas- 
urement or  by  weight.     A  2000-  3.  c.  graduated  cylinder  is  fre- 


92  GAS  AND  FUEL  ANALYSIS 

quently  used.  This  is  not  an  ideal  device,  for  not  only  are  the 
graduations  coarse  but  the  varying  temperatures  at  which  the 
water  is  measured  necessitate  the  use  of  different  correction 
factors  to  reduce  the  volumes  to  the  equivalent  weights.  It  is 
much  more  satisfactory  to  weigh  the  water.  If  the  thermomsters 
are  in  the  Fahrenheit  scale  it  is  more  convenient  that  the  balance 
shall  weigh  in  pounds  and  hundredths  of  a  pound.  If  the  ther- 
mometers read  in  the  Centigrade  scale  it  is  more  convenient  to 
preserve  the  metric  unit  throughout.  The  water  should  be 
weighed  in  a  metal  bucket  or  glass  vessel  for  which  a  counter- 
poise is  provided.  It  is  convenient  to  counterpoise  the  bucket 
with  the  interior  wet  as  it  is  just  after  the  water  has  been  poured 
out  after  a  test.  Its  weight  will  be  so  nearly  constant  that  it  is 
not  necessary  to  counterpoise  after  each  test.  The  balance 
should  be  capable  of  carrying  ten  pounds  on  each  pan  with  a 
sensitiveness  of  one-hundredth  of  a  pound. 

8.  Junkers'  Calorimeter. — The  original  form  of  Junkers' 
gas  calorimeter  is  shown  in  Fig.  22  and  the  improved  form  in 
Fig.  23.  The  Committee  on  Calorimetry  of  the  American  Gas 
Institute  suggested  that  the  older  type  of  Junkers'  calorimeter 
would  be  improved  if  the  inlet  and  outlet  thermometers  were 
brought  to  the  same  level  so  as  to  facilitate  rapid  reading  of  the 
two.  This  change  has  been  effected  in  the  improved  instrument 
but  it  is  claimed  by  some  observers  that  the  efficiency  of  the 
newer  type  is  not  so  high  as  the  older.  The  numbers  and  letters 
refer  to  the  same  parts  in  each  figure  and  the  same  description 
will  answer  for  both  of  these  instruments  as  well  as  for  others  of 
the  same  type  put  out  by  other  manufacturers.  The  gas  coming 
from  the  meter  is  burned  in  a  Bunsen  burner  placed  in  the  cylin- 
drical combustion  chamber  of  the  instrument.  The  hot  gases 
rise  in  the  central  chamber,  pass  down  through  a  series  of  small 
tubes  in  the  annular  water  jacket  surrounding  the  combustion 
chamber,  unite  again  in  a  single  flue  at  the  bottom  of  the  instru- 
ment and  pass  out  through  an  orifice  whose  size  may  be  regulated 
by  a  damper.  Water  enters  through  the  rubber  tube  w  to  the 
small  elevated  tank  a  which  serves  to  supply  water  to  the  cal- 
orimeter under  a  constant  head.  The  amount  of  water  flowing 
into  the  instrument  is  controlled  by  the  valve  b  and  the  waste 
water  from  a  is  discharged  at  c.  The  water  traversing  the  instru- 


HEATING  VALUE  OF  GAS 


93 


ment  passes  out  at  d  and  during  the  actual  test  is  measured  in 
the  graduated  cylinder  shown,  or  collected  in  a  vessel  and  subse- 
quently weighed. 

The  operation  of  the  instrument  is  shown  in  detail  in  Figs.  22 
and  23.     The  sectional  illustration  shows  the  burner  (2)  prop- 


FIG.  22a. — Junkers'  gas  calorimeter. 
Original  form. 


FIG.  22b. — Section  of  Junkers' 
gas  calorimeter.     Original  form. 


erly  placed  in  the  combustion  chamber  (1)  and  the  path  of  the 
combustion  gases  and  the  water.  The  products  of  combustion 
rise  in  the  central  chamber,  turn  at  the  top,  descend  the  annular 
cooling  chamber  (3)  to  the  drum  (4)  pass  the  thermometer  (5) 
and  escape  at  (6).  The  water  rises  to  the  small  overflow  cup  (7) 


94 


GAS  AND  FUEL  ANALYSIS 


traversing  a  filter  of  wire  gauze.  The  excess  of  water  overflows 
and  passes  out  of  the  instrument  to  the  waste  pipe  through  a 
rubber  tube  attached  at  (8).  The  small  vessel  (7)  must  always 
be  kept  overflowing  to  insure  a  constant  pressure  and  hence  a 


FIG.  23a. — Junkers'  improved  gas 
calorimeter. 


FIG.  23b. — Section  of  Junkers'  im- 
proved gas  calorimeter. 


constant  supply  of  water  through  the  valve  (9) .  The  water  pass- 
es the  thermometer  (10)  which  registers  the  inlet  temperature 
and  in  the  newer  form  of  instrument  descends  in  a  small  pipe 
within  the  outer  casing  to  the  bottom  of  the  instrument.  In 
both  forms  of  instrument  the  water  rises  in  the  annular  chamber 


HEATING  VALUE  OF  GAS  95 

surrounding  the  gas  passages  (3),  thus  passing  in  a  direction 
opposite  to  that  of  the  combustion  gases.  The  water  from  the 
annular  chamber  passes  through  the  drum  (11)  provided  with 
baffle  plates  to  mix  it  and  insure  that  all  parts  of  the  stream  are 
of  uniform  temperature,  passes  the  thermometer  (12)  which 
registers  the  outlet  temperature,  to  the  overflow  vessel  (13)  and 
out  at  (14). 

The  water  formed  in  the  combustion  of  the  hydrogen  and 
hydrocarbons  of  the  gas  is  condensed  as  it  descends  the  annular 
condenser  (3)  and  passes  out  of  the  drip  shown  at  (15)  and  at  e 
and  is  caught  in  a  graduated  cylinder.  The  working  parts  of  the 
calorimeter  thus  described  are  insulated  from  the  room  by  an 
air  jacket.  The  outer  casing  of  the  calorimeter  is  nickel-plated 
and  to  be  kept  polished  to  lessen  the  loss  of  heat  by  radiation. 
It  is  well  to  drain  the  calorimeter  when  not  in  use  by  opening  the 
cock  (16).  There  is  some  danger  that  air  brought  in  by  the  in- 
coming water  may  collect  around  the  inlet  thermometer  and 
disturb  the  accuracy  of  its  readings.  In  the  improved  form, 
the  tube  (h)  shown  at  the  top  of  the  calorimeter  in  Fig.  23  is  to 
allow  such  bubbles  to  escape.  Any  water  entrained  by  the  bub- 
bles passes  out  of  the  small  overflow. 

9.  Preliminaries  of  a  Test. — The  calorimeter  is  to  be  set  up 
on  a  table  where  the  light  is  good,  where  there  are  no  draughts, 
and  where  there  is  a  water  supply  and  a  waste  pipe.  Fig.  24 
shows  the  calorimeter  set  in  a  hood  which  has  been  modified  by 
lowering  a  portion  of  the  floor  to  bring  the  thermometer  more 
nearly  on  a  level  with  the  eye  of  the  observer.  On  the  top  of 
the  hood  is  a  zinc-lined  wooden  tank  connected  krthe  water 
supply  and  provided  with  an  overflow  pipe,  from  which  the 
water  supply  for  the  calorimeter  is  drawn.  This  large  overflow 
tank  is  advisable  as  it  compensates  for  variations  in  the  tempera- 
ture and  pressure  of  the  city  water  supply. 

The  first  step  is  to  turn  on  the  water  and  regulate  the  supply 
so  that  it  flows  through  the  instrument  at  the  rate  of  approxi- 
mately 1.5  to  2.0  liters  per  minute  in  case  illuminating  gas  of 
ordinary  quality  is  to  be  tested.  The  water  must  continuously 
overflow  from  both  cups  (13)  and  (8)  of  Figs.  22b  and  23b. 
No  water  should  drip  from  spout  (15)  nor  from  any  other  part 
of  the  instrument. 


96 


GAS  AND  FUEL  ANALYSIS 


The  gas  meter  is  to  be  levelled  and  more  water  added  if  neces- 
sary to  bring  the  bottom  of  the  meniscus  of  the  water  on  a  level 
with  the  pointer.  This  is  to  be  done  when  there  is  no  gas  pressure 
on  the  meter,  and  to  ensure  this  state  of  affairs  the  burner  cock 
on  the  outlet  of  the  meter  should  be  open  and  an  opening  should 
be  made  to  the  air  on  the  inlet  side  of  the  meter.  This  may 
usually  be  most  conveniently  effected  by  disconnecting  the  rub- 
ber tube,  but  may  also  be  accomplished  by  unscrewing  the  small 
plug  at  the  bottom  of  the  well  below  the  gas  inlet.  This  also 


FIG.  24. — Gas  calorimeter  and  accessories. 

serves  the  purpose  of  removing  any  water  which  may  have 
spattered  into  the  gas  inlet.  The  probable  error  in  adjusting 
the  water  level  is  0.3  per  cent,  so  that  when  a  greater  accuracy 
is  required  the  meter  should  be  recalibrated  after  adjustment. 
The  gas  supply  is  to  be  connected  to  the  meter  and  then  to  the 
calorimeter.  A  pressure  regulator  should  be  unnecessary  on  a 
city  gas  supply  if  the  meter  works  smoothly.  Directions  are 
frequently  given  to  interpose  a  regulator  of  the  floating  bell-jar 
type  between  the  meter  and  the  calorimeter.  If  this  is  done 


HEATING  VALUE  OF  GAS  97 

it  must  be  watched  closely  because  any  variation  in  the  heights 
of  the  drum  of  the  regulator  at  the  beginning  and  end  of  the  test 
causes  an  error  in  the  measurement  of  the  gas.  Long  connections 
of  rubber  tubing  are  to  be  avoided  since  rubber  is  porous  and  also 
exerts  a  selective  solvent  action  on  the  hydrocarbons  of  the  gas. 
The  connections  should  be  of  glass  with  short  lengths  of  rubber 
on  each  end. 

The  system  is  to  be  tested  for  leaks  by  closing  the  burner  cock 
and  opening  the  inlet  cock  on  the  gas  main.  The  large  hand  of 
the  meter  should  not  show  any  perceptible  change  in  position 
after  two  minutes.  When  the  system  has  been  found  to  be  tight 
the  burner  cock  may  be  opened  and  the  gas  allowed  to  escape 
into  the  air  of  the  room  until  the  large  hand  of  the  meter  has  made 
one  complete  revolution.  It  may  then  be  lighted  without  danger 
of  explosion  unless  the  gas  is  acetylene,  uncarburetted  water  gas 
or  similar  gases  having  wide  explosive  limits.  Be  sure  that  no 
unburned  gas  gets  into  the  calorimeter  where  it  might  cause  ex- 
plosion later. 

The  flame  from  the  burner  is  to  be  regulated  so  that  it  is  a 
clear  blue  color  with  just  a  tinge  of  yellow  at  the  tip.  The 
volume  will  depend  on  the  quality  of  the  gas.  Special  tips  for 
gases  of  very  high  or  low  heating  value  are  provided  with  the 
instrument.  With  ordinary  illuminating  gas  the  rate  of  flow 
should  be  between  5  and  7  ft.  per  hour.  The  gas  should  be  burned 
with  a  small  excess  of  air.  The  draft  may  be  controlled  by  the 
butterfly  valve  (6)  of  Figs.  22  and  23.  The  valve  should  be  set 
to  give  maximum  readings  of  the  thermometer  on  the  water 
outlet.  That  setting  which  gives  the  highest  result  is  the  most 
accurate.  The  flame  must  burn  perfectly  steadily.1  If  it  flickers 
the  most  probable  cause  is  the  presence  of  water  in  some  of  the 
connections.  The  rubber  tubing  should  be  disconnected  and 
drained,  the  plug  in  the  well  below  the  inlet  of  the  meter  removed, 
and  the  pressure  regulator  examined.  It  may  be  that  the  flicker- 
ing is  due  to  friction  within  the  meter  which  causes  the  drum  to 
stick.  This  can  usually  be  observed  by  closely  watching  the 
large  hand  of  the  meter  and  observing  if  it  lags  at  particular 
points  of  its  revolution.  Trouble  from  this  source  cannot 
usually  be  remedied  without  sending  the  meter  back  to  the  fac- 
tory. Flickering  of  the  flame  of  the  test  burner  may  also  be  due 


98  GAS  AND  FUEL  ANALYSIS 

to  fluctuations  in  the  pressure  of  the  gas  in  the  mains  or  services'! 


A  U-gage  attached  to  a  gas  outlet  will  show  whether  this  is 
case.  If  it  is  necessary  to  test  gas  under  these  conditions  the 
flickering  may  be  lessened  by  interposing  between  the  gas  outlet 
and  the  meter  a  large  empty  bottle.  Care  must  be  taken  to  fill 
this  bottle  completely  with  water  and  then  displace  this  with  gas 
to  avoid  danger  of  explosion. 

If  the  meter  has  been  recently  filled  with  fresh  water  the  gas 
should  be  allowed  to  burn  for  an  hour  before  the  test  in  order  that 
the  water  of  the  meter  may  become  saturated  and  not  cause  any 
change  in  the  composition  of  the  gas  passing  through  it. 

10.  Description  of  a  Test.  —  When  the  gas  and  water  supply 
and  the  burner  have  been  thus  adjusted,  the  lighted  burner  may 
be  placed  in  the  calorimeter,  care  being  taken  to  properly  center 
it.  This  operation  is  facilitated  by  a  small  mirror  placed  below 
the  instrument.  The  thermometer  in  the  outlet  water  will  at 
once  commence  to  rise,  and  in  a  few  minutes  will  be  constant  to 
within  a  few  tenths  of  a  degree.  The  increase  in  temperature  of 
the  outflowing  over  the  incoming  water  should  not  be  more  than 
10°  C.  and  it  may  be  necessary  to  readjust  the  water  and  gas 
supply  to  obtain  this  condition.  If  it  is  necessary  to  change  the 
adjustment  of  the  gas  the  burner  should  be  removed  from  the 
calorimeter.  The  butterfly  valve  must  not  be  closed  enough  to 
prevent  the  flame  from  burning  strongly  and  freely.  The  escap- 
ing gases  should  not  have  any  odor  of  unburned  gas.  Their 
temperature  should  be  only  a  few  degrees  above  that  of  the  water 
entering. 

The  water  formed  in  the  combustion  of  the  hydrogen  and 
hydrocarbons'  will  condense  in  the  calorimeter  and  commence 
to  drip  from  the  small  spout  at  the  bottom  of  the  instrument. 
The  test  should  not  be  commenced  until  the  thermometer  on  the 
water  outlet  has  remained  constant  for  several  minutes  and  the 
condensed  water  has  also  commenced  to  drip  from  its  spout 
showing  that  equilibrium  has  been  reached  within  the  calorimeter. 

The  counterpoised  bucket  for  the  water  is  placed  in  a  conve- 
nient position  and  as  the  large  hand  of  the  meter  passes  a  zero 
mark  the  water  is  turned  into  the  bucket.  Both  thermometers 
are  now  to  be  read  at  each  quarter  position  of  the  meter  hands  or 
more  frequently.  The  outlet  thermometer  sometimes  fluctuates 


HEATING  VALUE  OF  GAS  99 

rapidly  and  it  is  well  under  such  circumstances  to  read  it  as  many 
times  as  possible  so  as  to  obtain  a  fairer  average.  A  consumption 
of  0.2  of  a  cubic  foot,  or  two  revolutions  of  the  large  meter  hand  is 
sufficient  with  illuminating  gas.  The  last  thermometer  readings 
will  be  made  when  the  meter  hand  is  in  the  three-quarter  position. 
The  operator  then  watches  the  meter  while  holding  one  hand  on 
the  tube  through  which  the  outlet  water  is  flowing  and  as  the 
meter  hand  again  reaches  the  zero  he  swings  the  tube  out  of  the 
bucket,  thus  marking  the  completion  of  the  test.  After  the  water 
has  been  weighed  a  duplicate  test  may  at  once  be  started.  The 
procedure  is  the  same  in  case  the  water  is  to  be  measured  in  a 
graduated  cylinder  instead  of  being  weighed.  The  volume 
readings  of  the  cylinder  must  be  converted  into  grams  by  means 
of  the  table  in  §  6  of  Chapter  XVI  on  Manipulation  of  the  Bomb 
Calorimeter.  It  is  not  possible  to  read  the  volume  very  accu- 
rately in  a  wide  graduated  cylinder. 

The  water  of  condensation  dripping  from  the  instrument  is  to 
be  measured  to  allow  the  calculation  of  the  net  heating  value. 
It  is  accurate  enough  to  catch  the  water  formed  from  1  cu.  ft. 
in  a  50  c.c.  graduated  cylinder. 

In  case  the  temperature  readings  have  not  stayed  constant 
within  a  few  tenths  of  a  degree  during  the  test,  the  results  should 
be  discarded  and  an  attempt  be  made  to  better  the  conditions. 

If  for  any  reason  the  burner  goes  out  during  a  test  and  unburned 
gas  gets  into  the  instrument,  it  must  be  expelled  before  again 
lighting  the  flame.  This  may  readily  be  accomplished  by 
blowing  vigorously  through  the  escape  pipe  of  the  combustion 


11.  Calculation  of  Results. — The  heating  value  of  gas  is 
usually  expressed,  in  English  speaking  countries,  in  British 
thermal  units  per  cubic  foot  of  gas  measured  when  saturated 
with  moisture  at  60°  F.  and  under  a  barometric  pressure  of  30  in. 
of  mercury.  The  method  for  correcting  the  observed  volume  of 
gas  to  these  standard  conditions  has  been  described  in  §  3.  The 
factors  for  converting  cubic  centimeters  of  water  at  various  tem- 
peratures to  grams  are  given  in  §  6  of  Chapter  XVI.  A  Calory 
is  accurately  enough  defined  as  the  amount  of  heat  required  to 
heat  1  kg.  of  water  1°  C.,  and  a  British  thermal  unit  to  be  the 
amount  required  to  heat  1  Ib.  of  water  1°  F.  irrespective  of  the 


100  GAS  AND  FUEL  ANALYSIS 

absolute  temperature  of  the  water.     The  formula  for  calculation 
of  the  heating  value  is 

m(t'-t) 

XT  V  — 

V 

where  m  =  mass  of  water  heated 

t'  =  mean  temperature  of  water  flowing  out 
t  =  mean  temperature  of  water  flowing  in 
v  =  corrected  volume  of  gas  burned 

If  m  is  expressed  in  pounds,  t  in  degrees  Fahrenheit  and  v 
in  cubic  feet,  the  result  is  at  once  British  thermal  units  per  cubic 
foot. 

If  m  is  expressed  in  kilograms,  t  in  degrees  Centigrade  and  v 
in  cubic  feet,  the  result  is  in  the  hybrid  unit  Calories  per  cubic  foot 
which  may  be  corrected  to  British  thermal  units  per  cubic  foot  by 
multiplying  by  3.968. 

If  m  is  expressed  in  grams,  t  in  degrees  Centigrade  and  v  in 
liters  the  result  will  be  in  the  metric  unit,  small  calories  per  liter 
which  is  the  same  as  Calories  per  cubic  meter.  This  is  the  method 
of  reporting  heat  values  in  Germany  and  other  countries  which 
use  the  metric  system.  To  convert  Calories  per  meter  to 
British  thermal  units  per  cubic  foot  of  gas  measured  under  the 
same  condition  multiply  by  .1124.  In  scientific  work  the  heating 
value  of  a  gas  is  usually  reported  as  Calories  per  cubic  meter  of 
dry  gas  at  0°  C.  and  760  millimeters  pressure.  In  technical  work 
in  Germany  the  gas  volumes  are  usually  corrected  to  15°  C.  and 
760  mm.  pressure  which  makes  the  conditions  practically  the 
same  as  prevail  in  this  country. 

The  following  calculations  are  for  a  test  where  an  American 
meter  passing  0.1  cu.  ft.  per  revolution  and  provided  with  a  Fah- 
renheit thermometer  was  used,  while  the  calorimeter  ther- 
mometers were  of  the  metric  system  and  the  water  was  weighed 
in  kilograms. 

Meter  reading  at  start 21 . 200 

Meter  reading  at  close 21 . 400 

Meter  temp 71°  F. 

Barometer 29 . 8 

Correction  factor  for  temperature  and  pressure 0 . 965 

Correction  factor  for  meter 0 . 996 


HEATING  VALUE  9fr  QA8 

Temperature  of  water 

In  Out 

12.1°C.  21. 5°  C. 

12.1°C.  21. 5°  C. 

12. 2°  C.  21. 5°  C. 

12. 2°  C.  21. 6°  C. 

12. 2°  C.  21. 7°  C. 

12. 2°  C.  21. 7°  C. 

12.1°C.  21. 6°  C 


Average  .  12  .  16°  C.  21  .  60°  C. 

Rise  in  temperature  of  water  ....................  1  ...   9  .  44°  C. 

Weight  of  water  heated  ...........................   3  .  164  Kg. 

Temp,  of  waste  gases  ...........  .....................   66°  F. 

Room  temp  .........................................   72°  F. 

Gas  burned,  uncorrected  ........................  0.200  cu.  ft. 

Gas  burned,  corrected  .......   0.2X0.965X0.996=0.192  cu.  ft. 

„     A.  3.164X9.44X3.968 

Heating     value  ..............  -        —  oT92  —       —  =  617  B.t.u. 

Had  the  English  system  of  weights  and  measures  been  used 
throughout,  the  calculation  would  have  been  simplified  by  the 
elimination  of  the  factor  3.968  and  would  have  become 

Gas  burned,  corrected     =0.192  cu.  ft. 
Water  heated  =  6  .  97  Ib  . 

Rise  in  temp,  of  water  =17.0°  F. 

Heating  value  =  "  =  617  B.t.u. 


12.  Gross  and  Net  Heat  Values.  —  The  method  of  calcula- 
tion of  the  preceding  section  gives  the  amount  of  heat  which  would 
be  imparted  to  the  calorimeter  if  the  products  of  combustion 
were  cooled  in  the  instrument  to  the  temperature  of  the  gas  and 
air  which  were  burned  and  escaped  from  the  instrument  with  the 
same  amount  of  moisture  which  they  brought  to  it.  It  gives  the 
maximum  utilizable  heat  and  so  is  often  called  the  gross  heat 
value.  In  the  absence  of  any  specification  to  the  contrary 
the  term  heat  value  is  to  be  understood  to  mean  gross  heat 
value. 

In  most  industrial  operations  the  combustion  gases  are  not 
cooled  to  room  temperature  before  escaping  from  the  apparatus 


102  GA3  &ND  FUEL 


ANALYSIS 


and  therefore  some  of  the  heat  of  the  gas  is  wasted.  This  is  due 
to  a  lack  of  efficiency  of  the  apparatus  and  varies  with  individual 
conditions.  There  are  so  many  industrial  operations,  however, 
where  the  water  formed  in  combustion  escapes  as  steam  and  the 
latent  heat  of  steam  formation  is  so  large  when  compared  with  the 
amount  of  heat  required  to  raise  the  temperature  of  fixed  gases 
or  of  water  or  steam  through  moderate  temperature  intervals 
that  the  value  of  the  latent  heat  is  frequently  deducted  from  the 
gross  heating  value.  The  resulting  lower  value  is  called  the  net 
heating  value.  The  heat  absorbed  when  one  gram  of  water  at  100° 
C.  changes  to  steam  at  the  same  temperature  is  0.536  Calories. 
The  heat  absorbed  in  the  change  of  liquid  water  at  10°  C.  to 
vapor  at  10°  C.  is  very  closely  0.600  Calories.  This  latter  figure 
is  usually  employed  in  calculating  the  net  heating  value  which  is 
obtained  by  multiplying  the  number  of  cubic  centimeters  of  con- 
densed water  dripping  from  the  calorimeter  during  the  combustion 
of  a  cubic  foot  of  gas  by  0.6,  and  3.968  to  convert  into  British 
thermal  units  and  then  subtracting  this  value  from  the  gross 
heat  value  in  British  thermal  units  per  cubic  foot.  The  method 
of  calculating  the  net  heating  value  in  the  test  reported  in  the 
preceding  section  is  as  follows : 

Meter  reading  at  start 21 . 200 

Meter  reading  at  close 22 . 100 

Gas  burned 0.900  cu.  ft.  uncorrected 

Gas  burned  corrected,  0.9X0.965X0.996=0.86  cu.  ft. 

Condensed  water  collected,  21.8  c.c. 

21  8 
Condensed  water  formed  per  cu.  ft.  gas  ~g=25.4  c.c. 

Latent  heat  of  condensed  water  25.4X0.6X3.968  =  60  B.t.u. 
Net  heating  value  of  gas  617-60  =  557  B.t.u. 

13.  Accuracy  of  Method.— The  accuracy  of  the  Junkers 
Calorimeter  was  thoroughly  investigated  in  1905  by  Immenkotter1 
and  in  1908  and  in  subsequent  years  by  the  Committee  on  Cal- 
orimetry2  of  the  American  Gas  Institute  which  made  a  com- 
parative study  of  the  Junkers  Calorimeter  as  compared  with  other 

1  Jour,  fur  GasbeL,  48,  736. 

2Proc.  Am.  Gas  Inst.,  1908,  285;  1909,  148;  1912,  65. 


HEATING  VALUE  OF  GAS  103 

continuous  flow  instruments.     Both  investigations  agree  as  to 
the  substantial  accuracy  of  the  Junkers  calorimeter. 
The  sources  of  error  are  as  follows : 

1.  Registration  of  gas  volume. 

2.  Measurement  of  temperature. 

3.  Measurement  of  water  heated. 

4.  Incomplete  combustion. 

5.  Sensible  heat  and  uncondensed  water  vapor  escaping  in 
combustion  gases. 

6.  Heat  lost  by  radiation. 

Errors  in  Registration  of  Gas  Volume. — If  the  meter  is  in  good 
condition  and  is  calibrated  after  the  water  level  has  been  ad- 
justed the  error  of  the  meter  need  not  exceed  one-tenth  of  1  per 
cent.  If  these  precautions  are  neglected  the  error  may  be  large. 
The  error  of  observation  will  be  about  one  small  division  of  the 
large  scale  corresponding  to  1  part  in  200  or  0.5  per  cent,  error 
in  a  test  as  ordinarily  run. 

Errors  in  Measurement  of  Temperature. — If  the  thermometers 
are  accurately  calibrated,  the  water  supply  of  constant  tempera- 
ture and  the  consumption  of  gas  and  its  heat  value  constant  dur- 
ing a  test,  there  should  be  practically  no  instrumental  error.  If 
the  constancy  of  any  of  these  conditions  is  upset  there  will  be 
errors  due  partly  to  lag  in  the  thermometers  which  do  not  instantly 
respond  to  the  changed  condition.  An  error  which  is  negligible 
except  in  the  most  accurate  work  is  that  caused  by  the  different 
temperature  of  the  bulb  and  the  stem  of  the  thermometer.  There 
will  be  no  correction  for  the  emergent  stem  of  the  inlet  thermom- 
eter if  the  inlet  water  is  at  room  temperature.  If  the  room  temper- 
ature is  70°  F.,  and  the  temperature  of  the  outlet  water  is  90°  F., 
an  addition  of  from  0.07  to  0. 10°  F.,  should  be  made  to  the  observed 
reading  of  the  outlet  thermometer,  the  exact  amount  depending 
on  the  depth  to  which  the  stem  of  the  thermometer  is  immersed 
in  the  water.  Detailed  tables  giving  these  corrections  may  be 
found  in  the  Proceedings  of  the  American  Gas  Institute  for  1912 
and  also  in  a  pamphlet  published  by  the  American  Gas  Institute 
entitled  Directions  for  Erecting  and  Operating  Gas  Calorimeters. 
A  more  important  error  due  to  changed  conditions  during  a  test 
results  from  the  large  volume  of  water  always  contained  in  the 


104  GAS  AND  FUEL  ANALYSIS 

calorimeter.  The  Junkers  calorimeter  contains  approximately 
1500  grm.  of  water  so  that  if  a  2000  c.c.  cylinder  is  being  used  to 
catch  the  water,  it  will  have  become  three-quarters  full  before  any 
of  the  water  whose  temperature  at  the  inlet  has  been  taken  reaches 
the  thermometer  at  the  outlet.  It  will  be  evident  that  the  larger 
the  volume  of  water  in  the  calorimeter  the  greater  is  the  possible 
error  from  this  source.  The  error  in  making  a  single  reading  of 
the  thermometers  should  be  less  than  a  tenth  of  a  degree  and  the 
mean  error  of  a  series  of  seven  observations  should  not  be  over 
0.05°.  On  a  rise  of  ten  degrees  this  corresponds  to  0.5  per  cent. 
This  average  of  seven  readings  will  not  give  the  correct  mean 
temperature  of  the  water  unless  the  individual  readings  differ 
from  each  other  only  by  a  few  tenths  of  a  degree. 

Errors  in  Determination  of  Mass  of  Water  Heated. — If  the 
water  is  measured  in  a  two  liter  cylinder  the  error  of  the  ob- 
servation will  hardly  be  less  than  10  c.c.  or  0.5  per  cent,  and  may 
be  twice  as  great.  The  error  in  weighing  the  water  should  be  less 
than  0.1  per  cent,  but  an  error  of  a  second  in  terminating  the 
experiment  means  25  c.c.  of  water.  This  is  a  greater  time  error 
than  necessary  but  the  probable  error  in  this  process  will  be  0.5 
per  cent. 

Error  Due  to  Incomplete  Combustion. — When  the  calorimeter  is 
properly  adjusted,  this  error  should  vanish. 

Errors  Due  to  Sensible  Heat  and  Uncondensed  Water  Vapor 
Escaping  in  Combustion  Gases. — As  the  gases  pass  down  through 
the  calorimeter  they  meet  water  of  progressively  lower  tempera- 
ture until  just  before  leaving  the  calorimeter  they  are  surrounded 
by  water  of  the  temperature  recorded  by  the  inlet  thermometer. 
They  should  therefore  leave  the  instrument  at  a  temperature 
within  a  few  degrees  of  that  of  the  inflowing  water.  With  a 
theoretical  air  supply  the  error  from  this  loss  of  sensible  heat  in 
the  dry  gas  is  less  than  0.3  B.t.u.  per  degree  of  temperature 
difference  per  cubic  foot  of  gas  burned.  According  to  the  report 
made  to  the  American  Gas  Institute,1  the  actual  errors  observed 
as  due  to  this  source  were  only  0.5  B.t.u.  per  degree  per  cubic 
foot  even  when  the  temperature  of  the  inlet  water  was  far  from 
that  of  the  room.  The  actual  figures  recalculated  slightly  are 
given  below. 

1  Proc.  Am.  Gas  Inst.,  1909,  168. 


HEATING  VALUE  OF    GAS 


105 


Temp, 
inlet 
water 

Temp. 

exhaust 
gases 

Difference  between 
temp,  exhaust  gas 
and  inlet  water 

Error  in  heat  value 
due  to  sensible  heat 
of  dry  gases  of  com- 
bustion, B.t.u. 

Error  per 
degree  . 
difference 

Deg.  F. 

39 

45.6 

+6.6 

+3.7 

0.56 

49              54.2 

+5.2 

+2.7 

0.52 

59.6 

63.2 

+3.6 

+  1.8 

0.50 

70.4 

72.4 

+2.0 

+  1.0 

0.50 

80.5 

81.5 

+  1.2 

+0.3 

0.23 

89.3 

88.6 

-0.7 

-0.5 

0.70 

The  error  due  to  water  vapor  in  the  exhaust  gases  may  be 
more  serious.  The  exhaust  gases  always  leave  the  calorimeter 
saturated  with  water.  The  gas  burned  having  passed  through  a 
wet  meter  is  also  practically  saturated  with  water.  The  air  for 
combustion,  whose  theoretical  volume  for  illuminating  gas  is 
roughly  six  times  the  volume  of  the  gas,  and  whose  actual  volume 
may  be  twice  that,  is  drawn  from  the  room  and  may  vary  widely 
in  humidity.  The  maximum  error  which  can  thus  be  introduced 
may  be  indicated  by  the  following  calculation.  It  is  assumed 
that  one  volume  of  gas  is  burned  with  six  volumes  of  air  and  that 
the  volume  after  combustion  contracts  to  six  volumes.  The 
water  formed  in  combustion  will  remain  in  the  vapor  form  so  far 
as  the  gases  can  hold  it  and  the  remainder  will  condense  in  the 
calorimeter.  The  one  volume  of  gas  burned  entered  the  calor- 
imeter saturated  with  water  so  that  only  additional  water  to 
saturate  5  cu.  ft.  need  come  from  combustion.  The  weight  of 
water  vapor  per  cubic  foot  of  gas  will  vary  with  the  temperature 
as  shown  in  the  following  table. 

Wt.   vapor  in 
Temp.  mixed  cu.   ft. 

gas  and  vapor 

32°  F 0.000304  Ib. 

42°  F 0.000440  Ib. 

52°  F 0.000627  Ib. 

62°  F 0. 000881  Ib. 

72°  F 0.001221  Ib.  • 

82°  F 0. 001667  Ib. 

92°  F 0.002250  Ib. 

The  following  examples  will  serve  as  an  illustration  of  the  use 
of  these  figures. 


106  GAS  AND  FUEL  ANALYSIS 

(1)  Assume  that  the  air  enters  at  62°  and  50  per  cent,  saturated 
with  water  vapor,  the  gas  enters  at  62°  saturated  with  moisture 
and  the  exhaust  gases  escape  at  82°. 

Moisture  brought  in  6  cu.  ft.  air  at    0.00044  =  0.00264  Ib. 
Moisture  brought  in  1  cu.  ft.  gas  at    0.00088=0.00088  Ib. 

0.00352 

Moisture  carried  out  by  6  cu.  ft.  gas  at  0.00166  0.01000 
Excess   of   moisture   supplied   from    water   of 

combustion  0 . 00648  Ib . 

Latent  heat  =  1070  B.t.u.  per  Ib. 
Heat  lost  =0.00648X1070  =  6.9  B.t.u. 

This  is  an  unusually  large  error  since  there  is  no  need  of  letting 
the  exhaust  gases  escape  at  such  a  high  temperature.  If  they 
had  escaped  at  72°  the  error  from  this  source  would  have  been  only 
4.1  B.t.u.  If  they  had  escaped  at  62°  the  error  would  have  been 
only  1.9  B.t.u.  If  they  had  escaped  at  52°  or  10°  below  room  tem- 
perature the  error  would  have  been  almost  zero. 

This  error  is  present  in  almost  all  operations  but  when  care  is 
taken  to  have  the  temperature  of  the  exhaust  gases  a  few  degrees 
below  that  of  the  room  the  error  should  not  be  over  3  B.t.u. 
It  will  usually  make  the  result  too  low  but  in  cases  where  the  room 
is  warm  and  the  air  nearly  saturated  with  water  it  may  be  in  the 
other  direction. 

The  most  accurate  results  are  obtained  by  keeping  the  tempera- 
ture of  the  gas  and  the  exhaust  at  room  temperature  and  correct- 
ing for  the  humidity  of  the  air  according  to  the  following  table 
compiled  by  the  Bureau  of  Standards.1  Under  these  conditions 
the  error  will  be  about  1  B.t.u.  Before  using  this  table  the  humid- 
ity of  the  air  must  be  determined  as  directed  in  the  following 
Section.  The  corrections  are  expressed  in  B.t.u/s  and  are  to  be 
added  where  the  sign  is  +  and  subtracted  where  it  is  — . 

1  Proc.  Am.  Gas.  Inst.,  7,  223  (1912). 


HEATING  VALUE  OF  GAS 


107 


CORRECTIONS   TO   OBSERVED   HEAT   TO    GET   TOTAL   HEAT 

VALUE.     AIR,  GAS  AND  EXHAUST  MUST  BE  AT  THE 

SAME  TEMPERATURE 

If  7  volumes  of  air  per  volume  of  gas  are  used 


Humidity 
per  cent. 

Room  temperatures 

65° 

70° 

75°      |      80° 

85° 

90° 

10 

+4.8 

+5.7 

+6.7 

+7.9 

+9.2 

+  10.5 

20 

+4.1 

+4.9 

+5.7 

+6.8 

+7.8 

+  9.0 

30 

+3.4 

+4.1 

+4.7 

+5.6 

+6.5 

+  7.4 

40 

+2.7 

+3.2 

+3.7 

+4.5 

+5.2 

+  5.9 

50 

+2.0 

+2.4 

+2.8 

+3.4 

+3.8 

+  4.3 

60 

+  1.3 

+  1.6 

+  1.8 

+2.2 

+2.5 

+  2.8 

70 

+0,6 

+0.8 

+0.8 

+  1.0 

+  1.2 

+  1-2 

80 

-0.1 

±0.0 

-0.1 

-0.1 

-0.1 

-  0.3 

90 

-0.8 

-0.9 

-1.1 

-1.3 

-1.5 

-   1.9 

100 

-1.6 

-1.8 

-2.0 

-2.4 

-2.8 

-  3.4 

Loss  of  Heat  by  Radiation. — The  calorimeter  is  protected  against 
interchange  of  heat  with  the  outside  air  by  an  insulating  air 
chamber  enclosed  in  a  polished  metal  jacket.  The  efficiency 
of  this  protection  is  given  in  the  report  of  the  Committee  on 
Calorimetry  of  the  American  Gas  Institute  for  1908  as  99.5 
per  cent.  The  metal  jacket  should  be  kept  bright  in  order  to 
maintain  this  efficiency. 

Accuracy  of  the  Process  as  a  Whole. — None  of  the  various 
preceding  sources  of  error  need  amount  to  over  0.5  per  cent. 
They  will  partially  offset  one  another.  When  great  care  is  taken 
the  total  error  may  not  be  over  1  per  cent.  Under  ordinary 
conditions  it  is  not  safe  to  assume  that  the  error  will  be  less  than 
2  per  cent. 

14.  Determination  of  Humidity  of  Air. — The  following  direc- 
tions for  the  measurement  of  atmospheric  moisture  are  given  by 
the  U.  S.  Weather  Bureau.1  The  most  reliable  instrument  for 
this  purpose  is  the  sling,  or  whirled  psychrometer.  In  special 
cases  rotary  fans,  or  other  means,  may  be  employed  to  move  the 
air  rapidly  over  the  thermometer  bulbs.  In  any  case  satisfactory 
results  cannot  be  obtained  from  observations  in  relatively 
stagnant  air.  A  strong  ventilation  is  absolutely  necessary  to 
accuracy. 

1  U.  S.  Dept.  Agriculture,  W.  B.  No.  235,  Psychrometric  Tables. 


108 


GAS  AND.  FUEL  ANALYSIS 


a 


The  sling  psychrometer  consists  of  a  pair  of  ther- 
mometers, provided  with  a  handle  as  shown  in  Fig. 
25,  which  permits  the  thermometers  to  be  whirled 
rapidly,  the  bulbs  being  thereby  strongly  affected 
by  the  temperature  of  and  moisture  in  the  air.  The 
bulb  of  the  lower  of  the  two  thermometers  is  cov- 
ered with  thin  muslin,  which  is  wet  at  the  time  an 
observation  is  made. 

It  is.  important  that  the  muslin  covering  for  the 
wet  bulb  be  kept  in  good  condition.  The  evapora- 
tion of  the  water  from  the  muslin  always  leaves  in 
its  meshes  a  small  quantity  of  solid  material,  which 
sooner  or  later  somewhat  stiffens  the  muslin  so  that 
it  does  not  readily  take  up  water.  This  will  be  the 
case  if  the  muslin  does  not  readily  become  wet  after 
being  dipped  in  water.  On  this  account  it  is  de- 
sirable to  use  as  pure  water  as  possible,  and  also 
to  renew  the  muslin  from  time  to  time.  New  mus- 
lin should  always  be  washed  to  remove  sizing,  etc., 
before  being  used.  A  small  rectangular  piece  wide 
enough  to  go  about  one  and  one-third  times  around 
the  bulb,  and  long  enough  to  cover  the  bulb  and 
that  part  of  the  stem  below  the  metal  back,  is  cut 
out,  thoroughly  wetted  in  clean  water,  and  neatly  fitted 
around  the  thermometer.  It  is  tied  first  around 
the  bulb  at  the  top,  using  a  moderately  strong 
thread.  A  loop  of  thread  to  form  a  knot  is  next 
placed  around  the  bottom  of  the  bulb,  just  where 
it  begins  to  round  off.  As  this  knot  is  drawn  tighter 
and  tighter  the  thread  slips  off  the  rounded  end  of 
the  bulb  and  neatly  stretches  the  muslin  covering 
with  it,  at  the  same  time  securing  the  latter  at  the 
bottom. 

To  make  an  observation,  the  so-called  wet  bulb 
is  thoroughly  saturated  with  water  by  dipping  it 
into  a  small  cup  or  wide-mouthed  bottle.  The  ther- 
mometers are  then  whirled  rapidly  for  fifteen  or 
twenty  seconds;  stopped  and  quickly  read,  the  wet 
bulb  first.  This  reading  is  kept  in  mind,  the  psychrometer  imme- 


FIG.    25.— 

Sling    p  s  y- 
chrometer. 


HEATING  VALUE  OF  GAS  109 

diately  whirled  again  and  a  second  reading  taken.  This  is  re- 
peated three  or  four  times,  or  more,  if  necessary,  until  at  least 
two  successive  readings  of  the  wet  fculb  are  found  to  agree  very 
closely,  thereby  showing  that  it  has  reached  its  lowest  tempera- 
ture. A  minute  or  more  is  generally  required  to  secure  the  cor- 
rect temperature.  In  whirling  and  stopping  the  psychrometer 
the  arm  is  held  with  the  forearm  about  horizontal,  and  the  hand 
well  in  front.  A  peculiar  swing  starts  the  thermometers  whirling, 
and  afterward  the  motion  is  kept  up  by  only  a  slight  but  very 
regular  action  of  the  wrist,  in  harmony  with  the  whirling  ther- 
mometers. The  rate  should  be  a  natural  one,  so  as  to  be  easily 
and  regularly  maintained.  If  too  fast,  or  irregular,  the  ther- 
mometers may  be  jerked  about  in  a  violent  and  dangerous  man- 
ner. The  stopping  of  the  psychrometer,  even  at  the  very  highest 
rates,  can  be  perfectly  accomplished  in  a  single  revolution,  when 
one  has  learned  the  knack.  This  is  only  acquired  by  practice, 
and  consists  of  a  quick  swing  of  the  forearm  by  which  the  hand 
also  describes  a  circular  path,  and,  as  it  were,  follows  after  the 
thermometers  in  a  peculiar  manner  that  wholly  overcomes  their 
circular  motion  without  the  slightest  shock  or  jerk.  The  ther- 
mometers may,  without  very  great  danger,  be  allowed  simply  to 
stop  themselves;  the  final  motion  in  such  a  case  will  generally  be 
quite  jerky,  but,  unless  the  instrument  is  allowed  to  fall  on  the 
arm,  or  strikes  some  object,  no  injury  should  result. 

The  tables  from  which  humidity  may  be  calculated  form 
Table  IV  of  the  Appendix  and  give  the  data  for  a  barometric 
pressure  of  29.0  inches  of  mercury.  Their  use  is  illustrated  by 
the  following  example. 

Air  temperature  t  =  75.0°  F. 

Wet  bulb  reading  t'  =  66.0°  F. 

t-t'      =   9.0°  F. 

In  table  opposite  75°  in  column  9.0  is  found  63. 
Relative  humidity  =  63  per  cent. 

If  the  barometric  pressure  had  not  been  29  in.  a  slight  error 
would  have  been  introduced  whose  magnitude  may  be  judged 
from  the  following  examples  of  the  same  problem  at  different 
barometric  pressures. 


110  GAS  AND  FUEL  ANALYSIS 

Barometric  pressure  30  Relative  humidity  63 

Barometric  pressure  27  Relative  humidity  63 

Barometric  pressure  25  Relative  humidity  64 

The  Weather  Bureau  report  235  referred  to  above  gives  fuller 
tables  and  may  be  obtained  from  the  Bureau  for  10  cents. 

15.  Non-continuous  Water  Heating  Calorimeters. — In  the 
third  edition  of  his  Gas  Analysis,  Hempel  described  a  calorimeter 
where  a  volume  of  about  a  liter  of  gas  was  measured  in  a  glass 
cylinder,  passed  through  a  small  burner  and  burned  in  a  stream 
of  oxygen  within  a  calorimeter  containing  a  known  mass  of  water. 
The  rise  in  temperature  of  the  water  gave  the  data  for  the  calcu- 
lation of  heat  value,  after  the  instrument  had  been  calibrated  by 
the  combustion  of  hydrogen. 

The  Graefe  calorimeter  is  a  more  recent  commercial  instrument 
of  the  same  general  type  but  somewhat  larger.  The  instrument 
is  rather  crudely  constructed  and  allows  the  exhaust  gases  to 
escape  at  an  unduly  high  temperature  so  that  it  is  necessary  to 
calibrate  it  against  some  standard  calorimeter.  An  inherent 
defect  in  calorimeters  of  this  type  comes  from  the  increasing 
temperature  of  the  exhaust  gases  as  the  test  proceeds  and  the 
water  of  the  calorimeter  becomes  warmer. 

The  Parr1  calorimeter  aims  to  compensate  for  this  error  and 
errors  due  to  moisture  in  the  exhaust  gases  by  providing  two  du- 
plicate calorimeters,  one  of  which  runs  on  pure  hydrogen  while 
the  other  is  testing  the  unknown  gas.  The  variation  from  the 
correct  result  shown  by  the  hydrogen  calorimeter  is  taken  as  the 
correction  to  be  applied  to  the  other  result.  The  Committee  on 
Calorimetry  of  the  American  Gas  Institute  in  its  1912  report 
states  that  this  calorimeter  if  properly  operated  gives  correct 
results  but  that  it  is  rather  complicated  in  construction  and 
requires  more  skill  for  its  proper  operation  than  the  other  types. 
The  instrument  gives  gross  heating  values  only. 

The  Doherty  calorimeter  is  a  compact  instrument  which  meas- 
ures the  gas  in  an  annular  cylinder  surrounding  the  combustion 
chamber  and  its  water  jacket.  The  gas  is  displaced  by  the 
warmed  water  which  has  flowed  through  this  water  jacket  or  heat 
absorption  chamber,  and  thermometer  readings  are  taken  as  the 

1 J.  Ind.  and  Eng.  Chem.,  2,  337  (1910). 


HEATING  VALUE  OF  GAS 


111 


water  level  passes  fixed  points  on  the  gage  glass.  No  meter  is 
required  and  the  water  is  neither  weighed  nor  measured.  The 
Committee  on  Calorimetry  of  the  American  Gas  Institute  in 
its  1912  report  states  that  this  calorimeter  when  operated  properly 
gives  the  same  efficiency  as  the  Junkers  calorimeter. 

16.  Automatic  and  Recording  Gas  Calorimeters. — The  form- 
ula for  the  calculation  of  the  heating  value  of  a  gas  as  given  in 

§  11  of  this  chapter  is  H.V.  =  —         — .     It  is  evident  that  if  the 

ratio  — can  be  kept  a  constant  and  t  can  also  be  kept  constant 

that  the  heating  value  can  be  readily  determined  from  a  single 
reading  of  t'  or  can  be  continuously  determined  by  a  recording 
thermometer  showing  the  temperatures  of  the  outlet  water.  In 

the  Junkers  continuous  calorimeter  the  ratio  —  is  kept  constant 

by  passing  both  gas  and  inlet  water  through  meters  whose  drums 
are  geared  together  by  a  chain  forcing  them  to  always  rotate 
proportionately.  There  are  various  other  types  of  automatic 
calorimeters.  In  every  case  they  should  be  checked  occasionally 
by  a  direct  determination  with  a  standard  instrument. 

17.  Calculation   of   Heating  Value  from  Chemical   Composi- 
tion.— If  the  heat  value  and  the  proportion  of  each  constituent 
in  a  mixed  gas  were  accurately  known,  it  would  be  possible  to 
calculate  the  heating  value  oft  he  mixture  with  entire  accuracy. 
The  following  table  gives  the  usual  values  in  Calories  per  gram 
molecule   and   also   the  values   recalculated  by   Earnshaw^   to 
British  thermal  units  at  60°  F.  and  30"  of  mercury  pressure. 


Gas 

Formula 

Calories  per 
gram  molecule 

B.  t.  u.'spercu. 
ft.  at  60°  and  30" 

Hydrogen 

H2     

68,360 

326.2 

Carbon  monoxide 

CO 

67.960 

323  5 

Methane  

CH4  

211,930 

1009.2 

Ethane  :. 

C2H6  

370,440 

1764.4" 

Propane  
Butane 

C3H8  

529,210 
687,190 

2521.0 
3274.0 

Ethylene 

C2H4  

333,350 

1588.0 

Propylene 

C3Hfl  .    .  . 

492,740 

2347  2 

Butylene  
Acetylene 

C4H»  
C2H2  

650,620 
310,050 

3099.2 
1476  .  7 

Benzene.  . 

CfiHe. 

799,350 

3807.4 

[  Jour  Franklin.  7ns/.,  146,  161  (1898). 


112  GAS  AND  FUEL  ANALYSIS 

If  each  constituent  in  the  gas  were  known,  the  heating  value 
calculated  from  this  data  would  probably  give  accurate  results. 
However,  when  it  is  noted  that  among  the  olefines,  propylene 
has  a  heating  value  approximately  50  per  cent,  greater  than  ethy- 
lene,  and  butylene  a  heating  value  almost  double  that  of  ethylene 
it  will  be  seen  that  there  is  dangerous  latitude  for  arbitrary 
assumptions  as  to  the  constituents  of  the  olefines.  When  the 
"  illuminants "  as  reported  include  not  only  the  olefines  but  ben- 
zene the  error  involved  in  an  arbitrary  assumption  of  the  mean 
heat  value  becomes  still  greater.  The  varying  members  of  the 
methane  series  also  possess  widely  differing  heating  values. 
Earnshaw,  in  the  reference  cited  gives  an  analytical  method 
for  determining  the  mean  composition  of  the  olefines  and  for 
differentiating  between  methane  and  ethane.  The  method  is, 
however,  difficult  analytically,  and  the  results  when  obtained 
are  not  entitled  to  the  degree  of  confidence  which  pertains  to 
those  obtained  directly  in  a  calorimeter. 

The  probable  error  involved  in  this  method  of  calculating  the 
heating  value*  of  gas  (unless  Earnshaw's  complex  analysis  is 
followed  out)  is  about  5  per.  cent.  In  the  case  of  carburetted 
water  gas  it  is  still  higher.  In  the  case  of  producer  gas  where  the 
total  percentage  of  hydrocarbon  is  low  and  where  all  suspended 
tar  particles  have  been  removed  the  results  are  more  accurate. 


CHAPTER  VIII 
CANDLE  POWER  OF  ILLUMINATING  GAS 

1.  Introduction. — Photometry  deals  with  the  measurement  of 
the  intensity  of  light.     The  term  light  as  used  here  includes  only 
those  rays  which  excite  vision  in  the  human  eye,  which  thus 
necessarily  becomes  the  final  arbiter  in  photometric  tests.     The 
eye  cannot  estimate  absolutely  the  amount  of  light  which  stimu- 
lates it.     It  can  compare  roughly  the  intensity  of  illumination 
from  two  sources  and  it  can  determine  with  more  precision  when 
the  intensities  from  two  sources  are  the  same.     In  the  sense  in 
which  it  is  here  used,  photometry  consists  in  the  comparison  of 
two  lights,  one  of  which  is  a  standard.     The  photometer  is  a 
device  which  assists  the  eye  in  determining  when  the  two  lights 
are  of  the  same  intensity.     The  intensity  of  light  entering  the  pho- 
tometer is  changed  by  varying  the  distance  between  the  photom- 
eter and  the  light,  the  intensity  of  light  from  a  given  source  varying 
inversely  as  the  square  of  the  distance.     When  the  adjustments 
have  been  made  so  that  the  intensity  of  light  impinging  on  the 
photometer  from  the  two  sources  is  the  same,  as  shown  by  the 
equal  illumination  of  the  two  photometer  faces,  the  ratio  of  the 
unknown  light  to  the  standard  light  becomes  mathematically 
calculable  from  the  relative  distances  of  the  lights  from  the  point 
of  equal  illumination.     The  value  of  luminous  intensity  is  in 
English-speaking  countries  and  in  France  expressed  in  candle- 
power. 

2.  Method  of  Rating  Candle-power. — The  light  emitted  from 
a  single  incandescent  particle  would  illuminate  urfiformly  every 
point  of  an  enveloping  sphere  and  the  intensity  of  illumination 
might  be  measured  equally  well  at  any  point  on  the  sphere. 
When  the  light  to  be  measured  comes  from  a  surface  of  finite  size 
as  is  always  the  case  in  practice,  there  is  interference  with  the  free 
path  of  the  light  waves  from  a  single  particle  in  one  or  more  direc- 
tions so  that  the  illumination  of  the  enveloping  sphere  is  no  longer 

8  113 


114  GAS  AND  FUEL  ANALYSIS 

uniform.  It  is  possible  by  the  use  of  reflecting  mirrors  to  deter- 
mine the  illumination  at  various  points  on  the  circumference  of  a 
polar  circle  and  to  plot  from  this  data  a  curve  showing  the. dis- 
tribution of  light  at  various  angles.  Methods  of  this  sort  are 
often  resorted  to  in  a  study  of  illumination  where  it  is  desired  to 
determine  the  value  of  a  light  source  for  a  particular  purpose. 
This  method  is,  however,  rarely  followed  where  it  is  simply  a 
question  of  testing  the  quality  of  the  gas.  The  simpler  custom  of 
taking  the  horizontal  candle-power  given  by  a  conventionalized 
burner  under  conventional  conditions  as  indicating  the  value  of 
the  gas,  has  become  well  established. 

3.  The  Bar  Photometer. — The  bar  photometer  consists  of 
a  graduated  bar  which  carries  at  one  end  a  standard  light  and  at 
the  other  end  the  test  light.  Upon  the  bar  slides  a  carriage  with 
an  apparatus  for  comparing  the  illumination  from  the  two  sources. 
The  carriage  is  to  be  moved  back  and  forth  until  the  point  is 
found  where  the  illumination  from  the  two  lights  is  equal,  and  its 
position  on  the  graduated  bar  recorded.  If  now  the  distance  of 
the  comparison  box  from  the  standard  light  be  called  "a"  and 
that  from  the  unknown  light  "b, "  then  the  illumination  of  the 
unknown  as  compared  with  the  standard  light  is  expressed  by  the 
proportion, 

unknown  _  b2 

standard     a2 

There  are  many  modifications  of  this  type  of  photometer  but 
all  involve  the  four  essentials:  a  standard  light,  the  unknown 
light,  a  photometric  screen  and  a  means  of  measuring  the  distance 
of  each  light  from  the  comparison  box.  It  is  customary  to  have 
the  two  lights  fixed  at  opposite  ends  of  the  bar,  in  which  case  the 
sum  of  a+b  in  the  preceding  formula  is  a  constant.  Some- 
times however  the  standard  lamp  is  placed  on  a  sliding  carriage 
connected  by  a  rigid  link  with  the  photometric  screen  so  that  the 
distance  "a"  of  the  formula  becomes  a  constant.  A  modification 
of  the  bar  photometer  in  use  in  England  is  the  table  photometer 
where  the  two  lights  and  the  comparison  box  are  all  rigidly  fast- 
ened at  the  points  of  a  triangle.  Comparison  is  effected  by  vary- 
ing the  rate  of  combustion  of  the  gas  being  tested  until  equality 
of  illumination  is  reached.  Its  candle-power  is  then  mathematic- 


CANDLE  POWER  OF  ILLUMINATING  GAS  115 

ally  determined.     This  method  of  determining  candle-power  is 
not  in  use  in  Germany  or  America. 

The  various  essential  parts  of  a  bar  photometer  will  be  con- 
sidered separately  and  the  details  of  its  operation  will  then  be 
described. 

4.  Standard  Light. — The  early  photometrists  used  as  their 
standards  candles  of  varying  size.     In  1860,  the  English  parlia- 
ment adopted  as  standard  the  sperm  candle  7/8  in.  in  diameter 
and  burning  at  the  rate  of  120  grains  per  hour.     In  1884,  Hefner 
v.  Alteneck  brought  out  the  amylacetate  lamp  which  has  become 
the  most  generally  used  standard  for  testing  the  candle-power  of 
gas.     The  Harcourt  10  candle  pentane  lamp  was  proposed  in  1898 
and  has  been  adopted  as  the  official  source  of  light  by  the  Gas 
Referees  of  London.     It  has  many  advantages.     All  of  these 
flame  standards  vary  materially  in   candle-power  with  change 
in  atmospheric  conditions  and  are,  for  scientific  work,  to  be  cor- 
rected to  standard  conditions  of  temperature,  pressure,  humidity 
and  percentage  of  carbon  dioxide  in  the  air.     In  ordinary  work 
when  used  in  measuring  candle-power  of  gas  flames  they  are  how- 
ever not  thus  corrected  but  the  assumption  is  made  that  the  stand- 
ard light  and  the  gas  light  are  equally  affected  by  atmospheric 
conditions. 

The  only  satisfactory  standard  not  affected  by  atmospheric  con- 
ditions is  the  incandescent  electric  lamp.  Incandescent  lamps 
properly  aged  may  be  bought  with  the  certificate  of  the  Bureau  of 
Standards  and  furnish  the  most  reliable  photometric  standards 
when  used  under  proper  conditions.  These  conditions,  however, 
require  that  the  lamp  shall  be  supplied  with  current  at  perfectly 
definite  voltage  from  a  large  storage  battery  equipped  with  suit- 
able rheostats  and  electrical  measuring  instruments  so  that  the 
installation  is  an  expensive  one,  and  is  used  only  in  research 
laboratories.  When  the  incandescent  electric  standard  is  used 
in  the  photometry  of  gas  flames  correction  must  be  made  for  the 
effect  of  atmospheric  conditions  on  the  flame.  This  correction 
is  not  infrequently  as  much  as  ten  percent,  and  has  been  accu- 
rately determined  for  only  a  few  of  the  standard  lights. 

5.  Photometric  Units. — The  international  candle  is  the  common 
unit  of  intensity  in  England,  France  and  America,  having  been 
officially  adopted  by  agreement  of  the  government  standardising 


116  GAS  AND  FUEL  ANALYSIS 

laboratories  of  the  three  countries  in  1909.  Prior  to  that  date 
the  official  unit  in  this  country  had  nominally  been  the  British 
Parliamentary  candle  but  there  had  not  been  definite  agreement 
as  to  its  value.  In  Germany  the  photometric  unit  is  the  Hefner 
which  equals  0.90  International  Candles.  Conversely  1  Inter- 
national Candle  equals  1.11  Hefners.  The  history  of  the  adop- 
tion of  the  International  Candle  may  be  found  in  the  reports  of 
the  Bureau  of  Standards  and  in  the  Proceedings  of  the  American 
Gas  Institute.1 

Although  there  is  thus  an  international  unit  of  light,  the 
international  candle,  it  does  not  follow  that  this  unit  is  best 
obtained  by  burning  any  actual  candle.  In  fact  various  other 
standard  lights  are  preferable. 

6.  Standard  Candles.— In  1860  the  Gas  Referees  of  the  City 
of  London  adopted  as  their  unit  the  light  emitted  by  a  sperm 
candle  of  1/6  Ib.  weight  when  burned  at  the  rate  of  120  grains  per 
hour.  From  time  to  time  they  issued  specifications  for  the  manu- 
facture of  candles  to  fulfill  this  requirement  but  were  never  success- 
ful in  ensuring  uniform  quality  and  in  1897  entirely 'discontinued 
the  use  of  candles.  The  Dutch  Photometric  Commission  reported 
in  1894,  after  an  exhaustive  study,  that  the  average  light  from 
a  good  English  Parliamentary  candle  might  exceed  or  fall  below 
that  of  the  average  candle  by  nine  per  cent.  The  use  of  candles 
as  standards  is  deservedly  decreasing. 

When  candles  are  to  be  used  they  are  burned  on  a  candle 
balance  placed  on  the  photometer  bench.  A  simple  form  of 
balance  is  illustrated  in  Fig.  26.  A  long  candle  is  cut  in 
two  and  both  halves  used  simultaneously.  They  are  to  be  al- 
lowed to  burn  until  the  cups  have  formed  normally  and  the  wicks 
have  bent  over  till  the  tips  are  glowing  in  the  outer  flame.  The 
candles  are  then  to  be  turned  so  that  the  glowing  end  of  one 
wick  points  towards  the  photometer  and  that  of  the  other  points 
in  a  direction  at  right  angles  to  that  of  the  first.  They  should 
project  1  to  1 1/2  in.  above  the  holder  and  should  burn  clearly  and 
without  guttering.  When  all  is  in  readiness  ,  for  a  test,  .  the 
counterpoises  are  adjusted  so  that  the  candles  are  slightly  too 
heavy  for  a  perfect  balance.  As  they  burn  away. the  pointer 
on  the  scale  falls  and  as  it  passes  the  zero  mark  the  stop  watch  is 

1  Proc.  Am.  Gas  Inst.  2,  454,  528  (1907);  3,  403  (1903);  4,  78  (1909). 


CANDLE  POWER  OF  ILLUMINATING  GAS 


117 


started.  A  20-grain  weight  is  then  placed  on  the  pan  below  the 
candles  and  photometric  readings  are  made  each  half-minute. 
At  the  expiration  of  four  and  a  half  minutes  the  observer  returns 
to  the  candle  balance  and  stops  the  watch  when  the  pointer 
again  is  at  the  zero  mark,  indicating  that  the  20  grains  of  sperm 
have  been  burned.  If  the  candles  are  burning  at  exactly  the 
proper  rate  the  watch  should  show  that  exactly  five  minutes 
have  elapsed.  If  the  variation  in  the  amount  of  sperm  burned 
per  hour  is  not  over  5  per  cent,  from  the  standard  amount  it  is 
permissible  to  make  a  mathematical  correction,  the  assumption 


FIG.  26 — Candle  balance. 

being  that  the  light  evolved  is  in  direct  proportion  to  the  weight 
of  candles  burned.  If  the  observed  weight  of  sperm  burned  by 
the  two  candles  is  250  grains  per  hour  instead  of  240  the  value 

250 

of  the  light  is  said  to  be  2X047)  =  2. 08  candles.     If  the  deviation 

is  greater  than  5  per  cent,  the  test  must  be  rejected  and  a 
different  candle  used.  Improper  ventilation  and  too  high  a 
temperature  in  the  photometer  room  will  affect  the  burning  of  the 
candles.  This  subject  is  discussed  in  §  18. 

7.  The  Hefner  Lamp. — The  dimensions  of  the  Hefner  lamp 
have  been  rigidly  specified  by  the  German  Reichsanstalt1  which 

1  Jour,  fur  GasbeL,  36,  341  (1893). 


118  GAS  AND  FUEL  ANALYSIS 

will  certify  a  lamp  to  be  correct  if  it  is  mechanically  properly 
made  and  gives  a  light  which  does  not  differ  more  than  2  per  cent, 
from  the  official  lamp  of  the  Reichsanstalt.  The  construction 
of  the  lamp  is  shown  in  Fig.  27.  It  consists  of  a  brass  bowl 
into  which  a  head  screws  carrying  the  German  silver  wick  tube 
and  the  mechanism  for  controlling  the  height  of  the  flame. 
The  flame  height  is  determined  by  a  gage  which  clamps  to  the 
head-piece.  The  older  form  of  gage  shown  at  A  consists  of  two 
sights,  one  on  each  side  of  the  flame.  The  newer  Kruss  optical 
gage  shown  at  C  consists  of  a  ground  glass  screen  and  a  magnify- 


FIG.  27. — Hefner  lamp. 

ing  lens  which  allows  more  delicate  adjustment  of  the  flame  tip 
to  the  horizontal  line  across  the  gage.  Each  lamp  is  provided 
with  a  control  gage  shown  at  B  which  fits  over  the  wick  tube 
and  sits  squarely  on  the  head-piece.  With  the  control  gage  in 
this  position  and  the  lamp  level  an  observer  looking  toward  the 
light  should  see  through  the  openings  D  a  very  fine  ray  of  light 
less  than  0.1  mm.  wide  between  the  top  of  the  wick  tube  and  the 
control  gage,  and  looking  through  the  optical  gage  should  see 
the  cross-hair  in  exact  coincidence  with  the  broad  top  of  the 
control  gage.  The  wick  tube  is  screwed  into  the  head-piece 
and  if  it  becomes  necessary  to  change  its  height  the  control  gage, 


CANDLE  POWER  OF  ILLUMINATING  GAS  119 

inverted,  is  to  be  pushed  down  the  wick  tube  and  used  as  a  handle. 
The  exact  material  of  which  the  wick  is  made  is  not  of  importance 
but  it  must  fill  the  tube  snugly  but  not  tightly.  It  is  best  to  use 
only  that  furnished  by  the  manufacturers.  The  amyl  acetate 
must  be  of  good  quality  and  certified  to  be  fit  for  photometrical 
purposes.  The  German  Gas  Association  sells  properly  certified 
amyl  acetate  in  one  liter  bottles. 

In  using  the  Hefner  lamp  the  bowl  is  to  be  filled  about  two- 
thirds  full  of  amyl  acetate  and  after  the  wick  has  been  moistened 
by  capillary  action  it  is  to  be  screwed  somewhat  above  the  wick 
tube  and  cut  squarely  off.  The  lamp  is  then  to  be  lighted  and 
allowed  to  burn  at  least  ten  minutes  with  occasional  regulation 
of  the  flame  height  before  a  test  is  commenced.  The  temperature 
of  the  photometer  room  should  be  between  60°  and  70°  F.  The 
lamp  is  to  sit  on  a  horizontal  support  in  a  room  free  from  drafts 
and  adequately  ventilated. 

The  flame  height  of  the  Hefner  lamp  is  to  be  carefully  adjusted 
since  a  deviation  of  1  mm.  from  the  correct  flame  height  of  40, 
introduces  an  error  of  about  3  per  cent.  It  is  the  luminous  tip 
of  the  flame  which  is  to  be  40  mm.  high.  With  the  Kriiss  optical 
gage  the  frosted  glass  cuts  out  the  almost  colorless  outer  flame  so 
that  there  is  no  possibility  of  confusion.  With  the  older  Hefner 
gage  the  luminous  tip  should  appear  tangent  to  the  lower  edge 
of  the  sighting  plane. 

If  the  lamp  is  used  only  infrequently  it  should  be  emptied 
after  use  and  both  lamp  and  wick  should  be  washed  with  alcohol. 
It  is  wise  to  throw  away  the  old  amyl  acetate  and  clean  the  lamp 
in  this  manner  at  intervals  even  when  it  is  in  frequent  use  since 
the  amyl  acetate  decomposes  somewhat  on  standing.- 

The  Hefner  lamp  gives  a  light  of  0.9  international  candles 
when  burned  in  pure  air  under  760  mm.  barometric  pressure  and 
containing  8.8  liters  of  water  vapor  per  cubic  meter.  Although 
atmospheric  conditions,  must  be  controlled  and  correction  made 
in  exact  scientific  work  corrections  are  usually  omitted  in  taking 
candle-power  of  gas  on  the  assumption  that  atmospheric  condi- 
tions affect  the  Hefner  lamp  and  the  gas  burner  to  a  similar  de- 
gree. The  errors  involved  in  this  assumption  are  discussed  briefly 
in  §  18.  The  Hefner  lamp  is  a  very  widely  used  standard.  It  is 
portable,  cheap,  and  accurate.  Its  disadvantage  is  its  low  candle- 


120 


GAS  AND  FUEL  ANALYSIS 


power,  and  the  tendency  of  the  flame  to  flicker,  especially  at 
summer  temperature. 

8.  The  Pentane  Lamp. — The    10    candle    pentane    lamp  or 

Harcourt  lamp  was  adopted  as  stand- 
ard by  the  London  Gas  Referees  in 
1898. l 

Fig.  28  shows  this  lamp  with  some 
improvements  in  details  recommended 
by  the  Bureau  of  Standards  and  added 
by  the  American  manufacturers.  In 
this  lamp  air  entering  at  A  passes  over 
pentane  and  becomes  saturated  with 
pentane  vapor.  The  air-gas  so  formed 
descends  by  gravity  to  an  Argand 
burner  B  enclosed  in  a  metal  hood. 
The  flame  is  drawn  into  a  definite 
form  and  the  top  of  it  is  hidden  from 
view  by  a  long  brass  chimney  C.  The 
chimney  is  surrounded  by  a  larger 
brass  tube  D  in  which  air,  warmed  by 
the  chimney,  rises  and  descends 
through  the  tube  E,  which  is  also  the 
main  standard  of  the  lamp,  to  the  cen- 
ter of  the  Argand  burner  where  it  aids 
in  the  combustion  of  the  gas.  The 
lamp  may  be  obtained  with  the  cer- 
tificate of  the  Bureau  of  Standards. 

Before  using  the  lamp  the  satu- 
rator  is  to  be  filled  abou  ttwo-thirds 
full  of  pentane  and  both  cocks  on  the 
saturator  are  to  be  closed.  As  pen- 
tane is  very  volatile  and  mixtures  of  its  vapor  and  air  within 
certain  proportions  are  explosive  care  .must  be  taken  that  no 
flames  are  burning  in  the  room  while  the  lamp  is  being  filled. 
The  inner  chimney  above  the  burner  must  be  centered  by 
the  adjusting  screws,  turned  so  that  the  mica  window  is  away 
from  the  photometer  box  and  set  at  the  proper  height  by  plac- 
ing on  the  burner  the  47  mm.  block  which  accompanies  the 
1  Jour,  of  Gas  Lighting,  71,  1253  (1898). 


FIG.  28. — 10  candle  power 
pentane  lamp. 


CANDLE  POWER  OF  ILLUMINATING  GAS  121 

lamp,  and  lowering  the  chimney  till  it  rests  lightly  on  the  block. 
To  prepare  the  lamp  for  lighting,  open  the  outlet  cock  on  the 
saturator  and  the  drip  cock.  This  will  fill  the  feed  pipe  with  pen- 
tane  vapor  and  air.  Open  the  inlet  cock  on  the  saturator,  close 
the  drip  cock,  open  the  regulating  cock  at  the  burner  and  light  the 
gas  at  once.  It  requires  about  fifteen  minutes  for  the  flame  to 
become  constant  and  during  this  period  the  top  of  the  flame  should 
be  kept  approximately  on  the  cross  bar  of  the  mica  window. 
The  lamp  should  be  set  for  maximum  luminosity  which  condition 
is  attained  when  the  flame  is  just  high  enough  so  that  the  non- 
luminous  upper  portion  is  cut  off  from  the  photometric  screen  by 
the  chimney.  In  case  of  doubt  the  proper  setting  may  be  deter- 
mined by  lighting  the  gas  flame  at  the  other  end  of  the  bench 
and  determining  with  the  photometer  the  setting  of  the  lamp 
which  gives  maximum  illumination. 

In  leaving  the  lamp  after  a  test  both  the  inlet  and  the  outlet 
cocks  of  the  saturator  should  be  closed.  After  about  a  gallon  of 
pentane  has  been  burned  the  liquid  remaining  in  the  saturator 
should  be  emptied  out  and  thrown  away. 

9.  Secondary  Standards  of  Light. — The  Hefner  lamp,  the  10 
Candle  Pentane  lamp  and,  to  a  lesser  degree,  standard  candles 
are  primary  standards  since  they  are  readily  reproducible.  There 
are  various  secondary  standards  which  are  convenient  to  use 
when  frequent  candle-power  determinations  are  to  be  made  but 
which  must  be  standardized  at  intervals  by  direct  comparison 
with  a  primary  standard.  Most  of  these  standards  are  based  on 
the  fact  that  the  brightest  portion  of  a  lamp  flame  is  of  almost 
constant  luminosity. 

The  Edgerton  Standard  burner  consists  of  a  Sugg  "D"  burner 
provided  with  a  glass  chimney  1  3/4  in.  in  diameter  and  7  in. 
high.  Outside  of  this  glass  chimney  is  a  brass  sleeve  with  a 
horizontal  slot  13/32  of  an  inch  high  through  which  the  light 
passes  to  the  photometer.  This  is  nominally  a  five  candle-power 
standard  but  will  actually  vary  from  four  to  seven  candles. 
After  the  value  with  a  given  gas  has  been  fixed  it  will  not  vary 
much  if  the  candle-power  of  the  gas  feeding  it  does  not  vary  over 
two  candles.  The  chimney  must  be  cleaned  frequently  and  the 
lamp  restandardized  each  time  a  new  chimney  is  put  into  service. 

The  Elliot  lamp  is  a  student  lamp  of  special  design  with  a 


122 


GAS  AND  FUEL  ANALYSIS 


flat  wick  and  a  rather  large  chimney  and  a  screen  which  cuts  off 
all  but  the  desired  portion  of  the  flame.  The  lamp  uses  kerosene 
as  its  fuel  and  is  nominally  a  ten  candle-power  lamp.  Its  illu- 
minating value  with  a  single  lot  of  good  kerosene  is  of  very  satis- 
factory constancy. 

10.  Standard  Gas  Burners. — At  the  time  when  gas  testing 
commenced  to  be  standardized  the  Argand  burner  was  the  form 
in  common  use.  This  type  was  therefore  naturally  adopted  as 
the  standard.  It  was  also  recognized  that  it  was  only  right  to 


A-'" 


FIG.  29.— D  Argand 
burner. 


FIG.  30. — Metropolitan 
No.  2  Argand  burner. 


test  the  gas  in  a  burner  which  was  adapted  to  it  and  therefore 
various  standards  came  into  vogue  in  England,  such  as  the  Sugg 
D  Argand  illustrated  in  Fig.  29,  which  is  intended  for  gases 
of  less  than  16  candle-power.  The  Sugg  F  burner  is  intended  for 
gases  of  16-20  candle-power. 

In  1905,  in  connection  with  a  readjustment  of  the  price  and 
candle-power  of  the  gas  supplied  in  London  the  Gas  Referees 
were  directed  by  Parliament  to  use  a  burner  adapted  to  obtain 
from  the  gas  the  greatest  amount  of  light  when  burned  at  the 
rate  of  five  cubic  feet  per  hour.  In  accordance  with  these  instruc- 


CANDLE  POWER  OF  ILLUMINATING  GAS  123 

tions  the  Gas  Referees  adopted  the  Metropolitan  No.  2  Burner 
shown  in  Fig.  30.  This  burner  differs  from  the  older  types 
mainly  in  having  an  adjustable  air  supply  to  the  center  of  the 
burner.  The  burner  is  designed  for  all  qualities  of  gas  up  to  20 
candle-power.  When  lighting  the  burner  the  air  regulating  disc 
A  is  to  be  screwed  down  so  that  the  full  supply  of  air  passes  to  the 
burner,  and  the  burner  is  to  be  adjusted  to  approximately  the  five 
cubic  foot  rate.  After  allowing  it  to  burn  for  fifteen  minutes  to 
become  thoroughly  warm  the  gas  is  to  be  adjusted  carefully 
to  the  rate  of  5  cu.  ft.  an  hour,  after  which  the  air  regulator  is  to 
be  screwed  upwards  until  the  flame  rises  in  the  chimney  as  high 
as  possible  without  smoking.  The  Metropolitan  No.  2  Argand 
gives  results  materially  higher  than  the  ordinary  Argand  on 
gases  of  low  candle-power. 

Bray's  No.  7  Slit  Union  burner  is  frequently  used  with  car- 
buretted  water  gas  of  more  than  20  candle-power.  The  rate  of 
gas  consumption  is  as  usual  adjusted  to  5  cu.  ft.  an  hour. 

11.  The    Bunsen   and    Leeson    Photometric    Screens. — The 
Bunsen  photometric  disc  dates  from  1841  and  in  its  simplest 
form  consists  merely  of  a  sheet  of  paper  with  a  grease  spot  in  the 
center.     This  is  mounted  so  that  it  may  be  moved  back  and  forth 
between  the  two  lights.     When  looking  toward  the  stronger  light 
the  translucent  grease  spot  appears  bright.     As  the  carriage  is 
slowly  moved  away  from  the  stronger  light  the  constrast  between 
the  spot  and  the  surrounding  paper  diminishes  and  almost  dis- 
appears when  equality  of  illumination  is  reached.     If  the  carriage 
is  moved  still  further  in  the  same  direction  the  grease  spot  stands 
out  dark  against  the  white  background.     The  paper  screen  is 
usually  mounted  in  a  box  as  shown  in  Fig.  34  where  by  an 
arrangement  of  mirrors  the  observer  standing  in  front  of  the 
instrument  may  see  both  sides  of  the  screen  at  once.     This  form 
of  apparatus  is  still  frequently  used. 

The  Leeson  star  disc  is  a  modification  of  the  Bunsen  screen. 
It  consists  of  a  piece  of  opaque  paper  from  whose  center  is  cut 
a  star  and  which  is  pressed  between  two  sheets  of  translcuent 
paper.  It  is  a  decided  improvement  on  the  Bunsen  screen. 

12.  The  Lummer-Brodhun  Photometric  Screen. — This  is  a 
very  accurate  form  of  photometer  which  is  shown  diagrammatic- 
ally  in  Fig.   31   and    in    perspective    in   Fig.   32.     It   consists 


124 


GAS  AND  FUEL  ANALYSIS 


of  a  series  of  reflecting  surfaces  and  prisms  which  direct  light  rays 
from  the  two  sources  into  a  telescope  tube.  Light  entering  from 
the  two  opposite  sources  R  and  L  is  diffusely  reflected  by  the 


FIG.  31. — Diagram  of  Lummer-Brodhun  photometric  screen. 

opaque  plaster  of  paris  disc  P  onto  the  mirrors  MI  and  M2  and 
by  them  to  the  prisms  AB.     The  prism  A  has  most  of  its  hypothe- 


FIG.  32. — Lummer-Brodhun  photometric  screen. 

nusal  face  ground  away,  only  a  small  circular  plane  being  left  in 
the  center.  The  two  prisms  are  clamped  closely  together  and 
become  optically  homogeneous  over  this  small  circular  area  shown 


CANDLE  POWER  OF  ILUMINATING  GAS 


125 


FIG.  33.— Field  of 
Lummer  -B  r  o  d  h  u  n 
contrast  photomet- 
ric screen. 


at  ab.  Of  the  light  coming  from  L  only  that  reaches  the  telescope 
which  passes  through  this  circular  spot,  the  path  of  the  rays  being 
shown  from  L2.  Of  the  light  from  R,  that  which  strikes  the  spot 
ab  passes  on  undeflected  and  is  absorbed  by  the  black  walls  of  the 
box.  The  path  of  these  rays  is  shown  from  R2.  The  other  rays 
suffer  total  reflection  into  the  telescope  as  shown  in  the  rays  from 
Hi.  The  image  in  the  telescope  appears,  therefore,  as  a  circular 
spot  illuminated  from  L  in  a  circular  field  illuminated  from  R.  In 
this  equality  photometer  when  the  illumination  from  the  two 
sources  is  identical  the  spot  and  the  field  are 
not  to  be  distinguished  from  one  another. 

In  the  Lummer-Brodhun  contrast  photom- 
eter advantage  is  taken  of  the  physiological 
fact  that  the  eye  is  able  to  perceive  a  smaller 
degree  of  difference  in  contrast  than  difference 
in  brightness.  By  suitably  cutting  the  prisms 
the  image  in  the  telescope  is  divided  into  four 
portions  as  shown  in  Fig.  33.  In  this  figure 
the  shaded  trapezoidal  space  A'  is  illuminated 
from  the  same  source  as  the  shaded  semi-circular  area  A.  Simi- 
larly B  and  B'  are  illuminated  from  the  same  source.  However, 
although  the  areas  A  and  A'  are  illuminated  from  the  same  source, 
they  are  not  equally  illuminated,  for  through  the  interposition  of 
a  plate  of  glass  before  A'  it  receives  about  four  per  cent,  less  light 
than  A.  B'  is  in  the  same  way  and  to  the  same  degree  less 
brilliantly  illuminated  than  B. 

If,  now,  the  light  from  the  two  sources  is  exactly  the  same  both 
in  intensity  and  color  the  semi-circular  fields  A  and  B  will  be 
identically  illuminated  and  will  not  be  distinguishable  from  one 
another.  The  trapezoidal  figures  A'  and  B'  will  also  be  identi- 
cally illuminated  and  will  stand  out  with  the  same  relief  from  their 
respective  backgrounds.  This  can  only  happen  when  A  and  B 
are  equally  illuminated.  It  affords  a  more  sensitive  ocular  test 
of  the  equality  of  A  and  B  than  can  be  'obtained  by  comparing 
them  directly.  The  lights  at  the  two  ends  of  the  bench  are  never 
of  absolutely  the  same,  and  are  sometimes  of  a  widely  differing, 
color.  When  a  Welsbach  light  is  tested  against  the  Hefner  lamp 
the  field  illuminated  from  the  mantle  burner  is  a  clear  blue  color 
while  the  other  is  a  yellow.  The  eye  cannot  determine  with  much 


126  GAS  AND  FUEL  ANALYSIS 

accuracy  when  the  yellow  field  and  the  blue  one  are  illuminated 
to  the  same  extent,  but  it  can  determine  with  greater  accuracy 
when  the  yellow  trapezoid  A'  stands  out  from  its  blue  background 
with  the  same  distinctness  that  the  blue  trapezoid  B'  stands  out 
from  its  yellow  background.  The  eye  judges  slight  contrasts 
more  accurately  than  large  ones  and  therefore  it  is  most  sensitive 
when  the  photometer  is  almost  at  the  neutral  point.  It  is  well 
to  make  an  approximate  setting  for  equality  of  A  and  B  and  then 
focus  the  attention  on  the  contrast  between  the  trapezoids  and 
their  respective  backgrounds  and  complete  the  adjustment. 

13.  The  Flicker  Photometer. — In  the  various  forms  of  flicker 
photometer  the  light  from  each  source  is  presented  alternately 
and  rapidly  to  the  eye  by  means  of  revolving  discs  or  prisms  in 
the  photometer  box.     When  the  intensity  of  light  from  the  two 
sources  is  the  same  the  flicker  vanishes.     No  difficulty  is  experi- 
enced with  lights  of  varying  colors,  but  the  photometer  is  fa- 
tiguing to  the  eye  and  its  proper   adjustment  requires  consid- 
erable skill. 

14.  The  Gas  Meter. — The  meters  used  in  photometric  work 
are  of  the  same  general  type  of  wet  meter  as  those  described  in 
§  3  of  Chapter  VII  for  calorimetric  work.     They  must  be  cali- 
brated with  the  same  care  and  used  with  the  same  precautions. 
It  is  more  convenient,  however,  to  use  a  smaller  meter  which 
passes  only  1/12  cu.  ft.  per  revolution.     When  the  gas  is  being 
burned  at  the  rate  of  5  cu.  ft.  an  hour  this  meter  will  make  exactly 
one  revolution  a  minute.     The  dial  of  the  meter  is  graduated  into 
five  parts  with  finer  subdivisions.     An  observation  of  one  minute 
will  therefore  give  directly  the  uncorrected  gas  consumption  in 
cubic  feet  per  hour.     Great  care  must  be  taken  to  see  that  the 
water  of  the  meter  is  saturated  with  gas  of  the  sort  that  is  to  be 
tested,  for  the  "illuminants"  of  the  gas  are  relatively  soluble  in 
water  and  a  slight  change  in  their  percentage  makes  an  appreci- 
able difference  in  the  candle-power  of  the  gas. 

15.  The  Photometer  Bench  and  Its  Equipment. — The  preceding 
sections  have  discussed  the  various  types  of  standard  lights, 
burners  and  photometers  which  may  be  used.     It  is  evident  that 
wide  latitude  may  be  exercised  in  the  choice  of  units  and  the 
method  of  assembling  them  to  form  a  photometer  bench. 

The  details  regarding  the  length  of  bar,  type  of  standard  light, 


CANDLE  POWER  OF  ILLUMINATING  GAS 


127 


form  of  test  burner,  kind  of  comparison  box,  and  the  directions 
for  testing  are  in  some  cases  controlled  by  legal  enactment  and  are 
in  some  cases  matters  of  arbitrary  choice.  It  is  possible,  how- 
ever, to  trace  two  distinct  lines  of  influence,  the  English  and  the 
German.  Of  these  the  English  is  the  older  and  the  German  the 
more  scientific.  Modern  methods  of  testing  show  more  and  more 
the  grafting  of  German  methods  onto  the  English  stock.  It  is 
under  all  circumstances  necessary  that  the  meter,  standard  light, 
and  gas  burner  be  thoroughly  reliable.  The  photometric  screen 


FIG.  34. — Photometer  bench. 

may  be  of  cheaper  type  and  the  bench  itself  may  be  of  simple 
wooden  construction  with  the  scale  made  of  yard  sticks  joined 
together.  The  bar  most  commonly  used  in  America  is  60 
in.  long.  This  is  sufficiently  accurate  where  ordinary  gas 
flames  are  being  tested.  For  lamps  of  high  candle-power  longer 
bars  are  desirable. 

A  photometer  bench  frequently  used  is  shown  in  Fig.  34. 
At  the  right  hand  end  is  shown  the  meter  and  next  to  it  the  candle 
balances  in  position,  with  the  Edgerton  standard  burner  on  a 
swinging  arm  so  that  it  may  be  used  instead  of  the  candles.  At 


128  GAS  AND  FUEL  ANALYSIS 

the  left  hand  end  is  the  Argand  burner  for  the  gas  and  between 
the  two  the  bar  itself  with  its  screens  and  photometer.  The 
piping  for  the  gas  is  entirely  below  the  table  top  but  the  pressure 
regulators  and  gages  are  shown  above  the  table  at  the  back. 

Precision  photometers  usually  follow  the  German,  or  Reich- 
sanstalt,  pattern  in  which  the  bar  is  built  up  of  a  rigid  steel  track 
on  which  the  carriage  of  the  photometric  screen  travels.  The 
standard  light  and  the  test  light  are  usually  also  mounted  on  a 
travelling  carriage  with  provision  for  clamping  them  rigidly  at 
any  desired  point  of  the  bench.  The  length  of  the  bench  may 
thus  be  varied  at  will. 

16.  Details  of  a  Test. — The  details  of  a  test  will  of  course  vary 
with  the  equipment  of  the  photometer  bench  and  especially  with 
the  type  of  standard  light  employed.  Directions  for  the  use  of 
these  lights  have  been  given  in  preceding  sections.  In  the  follow- 
ing paragraphs  will  be  found  general  directions  which  are  appli- 
cable to  most  forms  of  apparatus. 

The  meter  is  to  be  examined  to  see  that  the  water-level  is 
correct  and  if  necessary  more  water  is  to  be  added.  In  case 
the  test  is  unusually  important  the  meter  should  be  calibrated 
against  a  tank  of  known  volume.  The  tightness  of  connections 
between  the  meter  and  the  burner  is  to  be  assured  by  turning  the 
gas  into  the  meter  while  keeping  the  stopcock  on  the  burner 
closed.  The  meter  hand  should  not  show  any  perceptible  motion 
in  one  minute.  If  there  is  a  small  leak  allowance  may  be  made 
for  it  in  the  calculations,  but  it  is  vastly  better  to  have  the  whole 
apparatus  tight. 

A  clean  chimney  is  to  be  placed  on  the  Argand  burner  and  the 
burner  lighted.  The  pressure  gage  between  the  diaphragm 
governor  and  the  burner  should  indicate  about  1  in.  of  water  pres- 
sure depending  on  the  exact  type  of  burner  used.  The  consump- 
tion of  gas  is  to  be  set  so  that  the  meter  hand  makes  a  revolution 
in  approximately  a  minute  and  the  light  is  then  allowed  to  burn 
for  at  least  fifteen  minutes.  If  the  meter  has  had  much  fresh 
water  added  to  it,  or  if  it  was  last  used  for  a  gas  of  a  different 
quality  than  the  one  soon  to  be  tested,  or  if  the  gas  is  being  drawn 
from  long  lengths  of  pipes  where  the  gas  lies  dead,  a  longer  time 
than  fifteen  minutes  must  be  allowed  to  elapse  before  commencing 
the  test  which  must  not  be  started  until  it  is  certain  that  the  gas 


CANDLE  POWER  OF  ILLUMINATING  GAS  129 

burning  is  of  representative  quality  and  that  it  has  not  been 
changed  by  contact  with  the  water  of  the  meter. 

The  final  adjustment  of  the  gas  is  made  after  taking  into  con- 
sideration the  meter  temperature  and  the  barometric  pressure. 
The  desired  rate  of  consumption  being  5  cu.  ft.  measured  under 
standard  conditions,  the  correct  apparent  rate  may  be  mentally 
calculated  by  adding  to  the  5  ft.  0.01  cu.  ft.  for  each  degree 
Fahrenheit  shown  by  the  meter  thermometer  above  60,  and  adding 
0.03  ft.  for  each  0.1  in.  of  mercury  pressure  below  30.  For  ex- 
ample, if  the  meter  temperature  is  80°  F.,  and  the  barometric 
reading  is  29.5  the  uncorrected  consumption  of  gas  per  hour  should 
be  5.0-f  .20+.15  =  5.35.  The  gas  is  to  be  set  to  this  desired  flow 
with  an  error  of  less  than  1/10  cu.  ft.  The  stop-watch  is  started 
as  the  hand  crosses  the  zero  and  stopped  after  one  complete  revo- 
lution. It  should  read  between  59  and  61  seconds.  After  the  gas 
has  been  satisfactorily  adjusted  and  the  standard  lamp  given  a 
final  adjustment  the  test  may  be  commenced. 

The  observer  starts  the  stopwatch  as  the  large  hand  of  the 
meter  passes  the  zero  and  steps  quietly  to  the  photometer  avoid- 
ing sudden  movements  which  would  create  drafts,  and  makes  and 
records  the  first  observation.  Four  more  readings  are  made  at 
intervals  of  about  twenty  seconds  and  then  the  photometric  screen 
is  reversed  and  five  similar  readings  taken.  If  the  lights  flicker 
during  an  adjustment  the  observer  must  wait  until  the  drafts  have 
subsided  before  completing  the  observation.  The  series  of  ten 
observations  usually  requires  about  five  minutes.  At  their  con- 
clusion the  operator  steps  back  to  the  meter  and  stops  the  watch 
as  the  large  hand  of  the  meter  again  passes  the  zero. 

If  a  stopwatch  is  not  available  it  is  better  to  make  the  test 
during  an  even  number  of  minutes  rather  than  during  the  con- 
sumption of  an  even  number  of  cubic  feet  of  gas.  If  the  observer 
holds  the  watch  close  to  the  meter  and  keeps  his  eyes  on  the  watch 
till  the  second  hand  reaches  the  zero  and  then  reads  the  position 
of  the  large  meter  hand,  and  follows  the  same  precedure  at  the 
close  of  the  test,  the  error  will  be  well  within  the  other  necessary 
errors  of  the  process.  In  case  a  stopwatch  is  available,  it  is  more 
accurate  to  start  the  watch  as  the  meter  hand  comes  to  its  zero 
and  to  conclude  the  observation  when  the  meter  hand  passes  its 
zero,  after  the  photometric  observations  have  been  completed. 


130  GAS  AND  FUEL  ANALYSIS 

17.  Illustration  of  Calculation. — The  calculation  which  follows 
is  for  a  test  made  on  a  2500  mm.  bench  with  a  Hefner  light  as  the 
standard. 

Date,  Feb.  26. 

Source  of  Gas.     Proportional  Tank.     Test  42.     Experimental  Gas  Plant. 

Gas  burned  in  London  Argand. 

Standard  Light — Hefner. 

Time  Meter  Reading 

Commencement  of  Test   10  :  16  :  00  A.  M.  47.8 

End  of  test  10:21:00  50+24.6  =  74.6 


Duration  5  :  00 

Cubic  feet  gas  uncorrected 26 . 8 

Cubic  feet  gas  per  hour  uncorrected 5 . 36 

Meter  Temperature  80°  F.     Error  in  meter  less  than  0.1  per  cent. 

Barometer  29.5  inches.     Correction  factor 0.973 

Cubic  feet  gas  per  hour  uncorrected  5 . 36.     Corrected 4 . 96 

Bar  Readings         454,  456,  455,  462,  460 

460,  458,  460,  463,  464  Average  462. 

[•(2500-462)2     XI      5.00 
Calculation       — f462>)2 =~9       4~~96 =      '     candle-power. 

18.  The  Photometer  Room. — The  photometer  bench  must  be 
placed  in  a  room  of  reasonably  constant  temperature  which  is 
free  from  drafts  and  yet  well  ventilated.  A  room  ventilated  so 
that  the  carbon  dioxide  does  not  rise  above  ten  parts  in  10,000 
during  a  test  is  as  much  as  can  be  expected  in  ordinary  work. 
The  carbon  dioxide  may  rise  to  twenty  parts  without  the  air 
being  more  polluted  than  in  an  ordinary  crowded  street  car  in 
winter.  The  water  vapor  normally  present  in  the  air  and  that 
given  off  by  the  flames  and  the  respiration  of  persons  in  the 
photometer  room  exerts  an  even  greater  influence  on  flames  than 
the  carbon  dioxide  but  since  its  accurate  determination  is  difficult, 
the  carbon  dioxide  is  usually  taken  as  the  measure  of  contamina- 
tion of  the  air. 

The  committee  on  Photometry  of  the  American  Gas  Institute1 
have  published  some  curves  showing  the  variation  of  certain 
flames  with  increased  carbon  dioxide  when  compared  with  an 
incandescent  electric  lamp.  The  humidity  of  the  air  varied  so 

iProc.  Am.  Gas.  Inst.,  11,  480  (1907). 


CANDLE  POWER  OF  ILLUMINATING  GAS  131 

much  from  day  to  day  that  a  comparison  of  one  day's  work  with 
another  could  not  be  made  and  the  following  figures  from  their 
curves  must  be  taken  as  merely  illustrative  of  the  large  errors 
that  may  arise. 

COMPARISON  OF  PENTANE  LAMP  WITH  GAS  FLAME 

Parts   CO2  in  10,000 10.0    20.6 

Per  cent,  loss  of  candle-power  gas  flame 4.0    20.0  • 

Per  Cent,  loss  of  candle-power  pentane 7.5    31.0 

COMPARISON  OF  PENTANE  LAMP  WITH  CANDLES 

Parts  CO2  in  10,000 10^0    20.0 

Per  cent,  loss  of  candle  power,  candles 19.0    27.0 

Per  cent,  loss  of  candle  power  pentane 13.0    16.5 

It  is  therefore  evident  that  the  usual  assumption  that  the 
standard  light  and  the  test  light  are  equally  affected  by  atmos- 
pheric conditions,  is  erroneous  and  that  care  should  be  taken  to 
have  the  test  made  under  as  favorable  atmospheric  conditions 
as  possible. 

19.  Jet  Photometers. — There  are  two  main  types  of  jet  pho- 
tometers.    In  one  type,  gas   passes  through   a  pressure  regu- 
lator and  issues  at  constant  pressure  through  a  small  round 
orifice  where  it  burns  in  a  jet  whose  height  as  read  on  the  glass 
chimney  is  assumed  to  give  candle  power  directly.     In  the  other 
type  of  jet  photometer  the  gas  flame  is  kept  at  a  constant  height 
and  the  pressure  required  to  force  the  gas  through  the  burner 
opening  is  measured  as  an  indication  of  candle  powers.     No  type 
of  jet  photometer  can  be  relied  on  to  do  more  than  give  approxi- 
mate  determinations.     They   should   be   calibrated   frequently 
against  a  bar  photometer. 

20.  Accuracy  of  Photometric  Work. — When  it  is  recollected 
that  the  Reichsanstalt  certifies  a  Hefner  lamp  as  correct  if  it  is 
within  2  per  cent,  of  their  standard,  and  that  the  absolute  value 
of  the  pentane  lamp  may  vary  as  much  as  25  per  cent.1  in  the 
course  of  a  year  on  account  of  changing  atmospheric  conditions 
and  further  that  the  human  eye  is  a  very  inaccurate  scientific 
instrument,  a  greater  accuracy  than  half  a  candle  can  hardly  be 

1  J.  B.  Klumpp,  Proc.  Am.  Gas  Light  Assoc.,  1905.     Appendix. 


132  GAS  AND  FUEL  ANALYSIS 

expected  with  illuminating  gas  tested  under  ordinary  conditions. 
Much  larger  errors  may  creep  in  unless  care  is  taken. 

The  determination  of  candle  power  has  largely  lost  its  signifi- 
cance as  a  criterion  for  municipal  gas  supplies,  since  from  75 
to  90  per  cent,  of  the  gas  sold  is  used  for  heating,  or  in  Welsbach 
burners,  where  the  heat  value  is  a  much  better  criterion.  The 
international  Photometric  Commission  in  1911  passes  the  follow- 
ing resolution.1 

11  The  International  Photometric  Commission  is,  after  consideration  of  the 
present  uses  of  illuminating  gas,  of  the  opinion  that  the  illuminating  value 
of  gas  flame  has  lost  its  significance  and  that  the  determination  of  the  heat- 
ing value  should  replace  the  determination  of  candle  power  as  the  most 
important  criterion  of  its  value." 

1  Jour,  fur  Gasbel,  1911,  1002. 


CHAPTER  IX 
ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS 

1.  Introduction. — The  estimation  of  particles  held  in  suspen- 
sion in  gases  is  daily  becoming  of  greater  importance  on  account 
of  legal  restrictions  on  pollution  of  the  air  and  on  account  of 
insistence  on  closer  control  of  industrial  operations  by  manu- 
facturers.    The  problem  is  one  of  great  difficulty  and  is  usually 
susceptible  or  only  approximate  solution.     Not  only  is  it  difficult 
to  obtain  the  suspended  solids  present  in  a  flue  at  a  given  point 
and  time,  but  it  is  difficult  to  determine  whether  the  solids  thus 
determined  were  normal  in  amount  or  whether  they  were,  for 
instance,  low  because  of  the  deposition  of  an  unusually  large  pro- 
portion prior  to  the  point  of  sampling  on  account  of  slower  veloc- 
ity of  gas  in  the  main,  or  because  of  lower  temperature  or  for  some 
other  reason. 

2.  The  Distribution  of  Particles  in  the  Cross-section    of   a 
Straight  Main. — If  the  main  is  horizontal  it  is  evident  that  there 
will  tend  to  be  a  stratification  of  the  particles,  the  large  and  heavy 
particles  separating  faster  than  the  fine  and  light.     This  tendency 
to  settle  is,  however,  resisted  by  the  whirling  motion  which 
gases  traversing  flues  frequently  possess  and  which  is  frequently 
caused  by  the  inequalities  in  pressure  produced  by  bends  in  the 
pipe.     The  velocity  of  gas  in  a  straight  main  at  ordinary  working 
speeds  is  greatest  at  the  center  and  least  at  the  walls.     The 
shape  of  the  wave  front  varies  with  the  speed  of  the  gas,  high 
velocities  accentuating  the  difference.     Solid  particles  are  pushed 
gradually  out  of  the  zone  of  high  velocity  into  one  of  lower 
velocity  in  the  same  way  that  a  piece  of  wood  in  a  river  is  grad- 
ually pushed  to  the  still  waters  along  the  bank.     This  action 
takes  place  in  a  vertical  as  well  as  a  horizontal  main. 

The  solids  contained  in  a  gas  at  the  point  of  greatest  velocity 
will  therefore  be  the  least  in  amount,  the  smallest  in  size,  and  the 
lowest  in  specific  gravity.  The  quantity  of  particles,  their  size 
and  specific  gravity  will  all  increase  in  the  regions  where  velocity 

133 


134  GAS  AND  FUEL  ANALYSIS 

is  least.  In  a  normal  round  main  this  point  of  greatest  velocity 
is  the  center  where  will  be  found  the  fewest  and  lightest  solid 
particles.  Their  quantity  and  magnitude  increase  in  successive 
rings  to  the  circumference.  If  the  velocity  of  the  gas  is  decreased 
until  the  main  is  also  acting  as  a  settling  chamber  there  will  be 
little,  difference  in  the  velocity  throughout  the  cross-section  and 
the  region  near  the  top  of  the  main  will  contain  the  fewest  solid 
particles. 

This  uneven  distribution*  of  suspended  particles  in  a  gas 
stream  may  take  place  very  rapidly  as  was  shown  by  the  author1 
some  years  ago  in  an  attempt  to  determine  the  amount  of  sus- 
pended tar  in  unpurified  illuminating  gas.  A  14-in.  main  con- 
taining unpurified  illuminating  gas  was  tapped  on  its  horizontal 
axis  at  a  point  a  few  feet  beyond  the  exhauster  and  two  sampling 
tubes  inserted,  one  extending  to  the  middle  of  the  main  and  the 
other  projecting  through  the  wall  only  about  an  inch.  Four 
tests  were  made  and  in  each  case  the  suspended  tar  caught  in  the 
sampling  tube  near  the  edge  of  the  main  was  more  than  twice  as 
great  as  that  found  in  the  tube  projecting  to  the  center. 

3.  Mean  Velocity  in  the  Cross-section  of  a  Gas  Main. — Threl- 
fall2  has  shown  that  it  is  necessary  to  investigate  the  distribution 
of  velocity  for  each  individual  case  as  it  arises,  but  that  in  general 
the  radius  of  the  circle  of  mean  velocity  is  about  0.775  of  the  ra- 
dius of  the  pipe.     In  one  case  it  was  as  high  as  0.9  of  the  radius  but 
in  no  case  did  it  sink  to  0.69  which  is  the  figure  quoted  for  water 
flowing  through  a  long  and  smooth  pipe.     The  radius  of  mean 
velocity  did  not  change  with  varying  speed  of  gas  flowing  through 
the  pipe  within  the  ranges  of  600  ft.  and  3600  ft.  per  minute, 
which  marked  the  limit  of  the  experiments.     Threlfall's  experi- 
ments were  on  pipes  varying  from  6  to  36  in.  in  diameter. 

4.  Influence  of  Bends  in  a  Main. — If  gas  flowing  through  a 
straight  main  comes  to  a  bend  there  will  be  a  change  in  the  rela- 
tive velocities  of  the  particles  of  the  gas  throughout  the  cross- 
section.     The  kinetic  energy  of  a  body  is  represented  by  the 
expression  l/2mv2  where  m  represents  the  mass  of  a  body  and  v  its 
velocity.     It  is  evident  therefore  that  the  particles  with  the 
greatest  mass  and  the  greatest  velocity  will  be  projected  beyond 

lProc.  Mich.  Gas.  Ass.,  1906. 
2Proc.  Inst.  Mech.  Eng.,  1904,  1,  245. 


ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS     135 

their  companions.  The  point  of  maximum  velocity  will  shift 
from  the  center  to  a  point  nearer  the  opposing  wall  and  will  then 
slowly  return  to  its  normal  position  with  a  spiral  movement. 
Solid  particles  on  account  of  their  greater  mass  may  strike  the 
opposing  wall  and  if  they  or  the  wall  are  sticky  may  adhere  there 
and  build  up  deposits. 

It  will  be  evident,  from  what  has  preceded,  that  it  will  not  be 
possible  to  find  a  single  point  in  a  gas  main  from  which  it  is  pos- 
sible to  draw  a  fair  sample  of  gas  for  the  determination  of  sus- 
pended solids.  If  a  sample  can  only  be  taken  at  a  single  point, 
the  termination  of  the  sampling  tube  should  be  at  about  the  point 
of  mean  velocity,  as  explained  in  the  preceding  section.  In  im- 
portant tests  it  is  advisable  to  draw  a  number  of  samples  from 
various  points  in  the  cross-section  of  the  main.  A  tube  with  nu- 
merous perforations  along  its  length  is  useless  for  this  work.  -  Sep- 
arate tubes  should  be  used  each  with  its  own  filter  and  aspi- 
rator as  explained  in  Chapter  I. 

5.  Velocity  of  Gas  in  a  Sampling  Tube. — The  rate  of  flow 
through  the  sampling  tube  has  a  ma- 
terial effect  on  the  accuracy  of  sam- 
pling as  has  also  the  inclination  of  the      


sampling  tube  to  the  gas  stream.     It     — »  ^^ 

is  evident  that  if  a  sampling  tube  is       ^        \ 

inserted  at  A  of  Fig.  35  at  right  angles 
to  the  flow  of  gas,  even  assuming  that 
the  solid  particles  are  uniformly  dis- 
tributed, the  result  will  be  incorrect        FlG   35._Diagram  show_ 
for  the  heavy  particles  will  tend  to  be     ing  method  of  inserting  sam- 
carried  past  the  open  end  of  the  tube     pling  tube  in  gas  main, 
and  not  drawn  into  it.     The  suspended 

solids  will  be  reported  low  even  if  the  speed  of  gas  within  the  sam- 
pling tube  is  as  high  or  even  higher  than  that  in  the  main.  If;  on 
the  other  hand,  the  opening  of  the  sampling  tube  faces  the 
approaching  stream  of  solid  particles  as  at  B,  on  the  same  assump- 
tion of  uniform  distribution  of  particles,  the  result  may  be  cor- 
rect, or  it  may  be  high  or  low.  If  the  speed  of  the  gas  in  the  sam- 
pling tube  is  the  same  as  that  in  the  main  the  result  should  theo- 
retically be  correct.  The  whole  column  of  gas  opposite  the  open- 
ing of  the  tube  should  enter  without  distortion.  If,  however,  the 


136  GAS  AND  FUEL  ANALYSIS 

velocity  in  the  sampling  tube  is  lower  than  that  in  the  main 
the  column  of  gas  approaching  the  opening  will  be  disturbed  and 
part  of  it  will  be  forced  aside.  The  solid  particles  will  on  account 
of  their  momentum  not  be  pushed  aside  so  readily  and  will  there- 
fore enter  the  tube  in  unduly  great  amount,  giving  a  high  result. 
If  the  velocity  of  the  gas  in  the  sampling  tube  is  greater  than  that 
in  the  main  there  will  again  be  a  disturbance  in  the  approaching 
column  of  gas.  A  column  of  gas  larger  than  the  opening  of  the 
tube  will  be  sucked  in,  but  the  solid  particles  in  the  outer  shell 
of  gas  thus  sucked  in  will  not  be  diverted  from  their  course  and 
will  pass  by  the  opening  of  the  tube,  giving  a  low  result.  Brady1 
states  that  in  sampling  blast-furnace  gas  an  error  of  more  than 
44  per  cent,  was  caused  when  the  sampling  speed  was  dropped  to 
half  that  in  the  main.  It  is  thus  evident  that  the  speed  with 
which  gas  enters  the  sampling  tube  must  be  carefully  controlled. 
The  velocity  of  the  gas  must  however  be  reduced  before  it 
passes  through  the  filtering  medium  or  the  finely  divided  particles 
will  not  be  taken  out.  The  usual  sampling  tube  has  therefore  a 
relatively  small  aperture.  Care  must  be  taken  that  the  aperture 
is  not  so  small  that  it  will  become  clogged,  which  readily  happens 
when  tarry  matters  are  present.  Each  case  must  be  studied 
independently. 

6.  The  Filtering  Medium. — Where  conditions  permit,  filter 
paper  discs  or  shells  make  satisfactory  filtering  media.  The 
Brady  gas  filter  for  dust  in  blast-furnace  gas  is  described  in  the 
article  referred  to  in  the  preceding  section.  A  filter  using  a  disc 
of  filter  paper  as  developed  by  Mr.  W.  S.  Blauvelt2  of  the  Semet- 
Solvay  Company  has  been  used  by  the  author  with  good  results. 

When  large  amounts  of  tar  are  present  a  weighed  tube  filled 
with  a  fibrous  material  may  with  advantage  be  inserted  ahead  of 
the  filter  paper.  The  filtering  materials  to  be  inserted  in  the  sam- 
pling tube  will  vary  with  conditions.  If  the  temperature  is  high, 
sand  or  ignited  asbestos  is  suitable.  Ignited  asbestos  is  usually  to 
be  preferred  since  on  account  of  its  fibrous  nature  it  makes  a  more 
efficient  and  a  lighter  filter.  This  last  consideration  is  of  impor- 
tance since  the  suspended  solids  collected  frequently  weigh  only 
a  few  milligrams  and  it  conduces  to  accuracy  to  have  the  increase 

1  Jour.  Ind  and  Eng.  Chem.,  3,  662  (1911). 
2Proc.  Am.  Gas.  Inst.,  4,  795  (1909). 


ESTIMATION  OF  SUSPENDED  PARTICLES  IN  GAS      137 

in  weight  of  the  filter  relative  to  its  initial  weight  as  large  as  may 
be.  The  tubes  may  be  of  glass,  porcelain  or  quartz  protected  if 
desirable  by  an  iron  jacket.  The  tubes  after  filling  and  before  use 
should  be  placed  in  an  air  bath  heated  to  the  temperature  to  which 
they  are  to  be  exposed  later  and  dry  air  should  be  drawn  through 
them  until  they  are  constant  in  weight.  They  should  then  be 
cooled  in  dry  air,  weighed,  carefully  stoppered  and  if  possible 
kept  in  a  dessicator  until  used.  The  asbestos  for  this  purpose 
should  not  be  soft  enough  to  pack  readily  and  choke  the  tube. 
The  fine  washed  asbestos  used  for  analytical  work  is  not  so  good  for 
this  purpose  as  a  cruder  sort.  Sometimes  when  much  tar  is 
present  it  is  advantageous  to  procure  the  crude  asbestos  rock  and 
merely  crush  it  coarsely  in  an  iron  mortar. 

7.  Estimation  of  Suspended  Tar  and  Water. — The  amount 
of  suspended  matters  caught  by  a  filter  paper  may  be  estimated 
either  by  color  or,  if  sufficient  in  amount,  may  be  determined  by 
weight.     A  second  weight  after  drying  at  105°  C.  for  an  hour  will 
give  by  difference  the  moisture  and  other  volatile  matter,  while 
the  weight  after  ignition  will  give  the  mineral  matter,  correction 
being  made  if  necessary  for  the  change  in  composition  due  to 
ignition. 

Where  asbestos  filters  have  been  used  a  smiliar  procedure  may 
be  followed  provided  the  asbestos  has  been  ignited  before  use. 
In  drying  the  tube  however  it  is  not  sufficient  to  heat  it  externally. 
Dry  air  must  be  drawn  through  until  it  comes  to  constant  weight. 
The  water  will  be  driven  off  and  also  approximately  25  per  cent, 
of  the  weight  of  the  tar.  The  non-volatile  tar  remaining  may 
afterward  be  extracted  with  chloroform  or  carbon  bisulphide, 
and  this  figure  increased  by  one-third  will  -give  a  rough  estimate 
of  the  amount  of  tar  present.  It  is  not  possible  to  determine 
accurately  the  amounts  of  water  and  suspended  tar  since  it  is  not 
feasible  to  determine  how  much  of  the  material  volatilized  is  tar 
and  how  much  is  water. 

8.  Electrical   Precipitation   of   Suspended   Particles. — Where 
the  expense  warrants  the  installation  of  the  process,  the  method  of 
electrical  precipitation  as  developed  on  the  large  scale  so  success- 
fully by  Cottrell1  may  be  applied.     The  equipment  consists  of  a 
small  step-up  autotransformer  capable  of  giving  15,000-30,000 

1  Jour.  Ind.  and  Eng.  Chem.,  3,  542,  (1911). 


138  GAS  AND  FUEL  ANALYSIS 

volts,  a  rotating  switch  to  rectify  this  high-tension  alternating 
current  and  a  precipitating  vessel  which  may  be  made  of  an  iron 
pipe  with  an  insulated  electrode  in  the'  center  An  exhauster 
for  aspirating  the  gas  and  a  meter  for  measuring  it  must  also 
be  provided.  This  apparatus  will  quantitatively  precipitate  all 
suspended  solid  and  liquid  bodies  including  tar  and  operates  on 
such  large  amounts  that  the  precipitated  materials  can  readily  be 
examined. 


CHAPTER  X 
CHIMNEY  GASES 

1.  Introduction. — A   knowledge  of  the  chemical  composition 
of  the  gases  escaping  from  a  chimney  aids  much  in  controlling 
the  efficiency  of  the  furnace.     It  makes  very  little  difference 
whether  the  fuel  is  burned  to  raise  steam  or  to  melt  steel  and  it  is 
of  equally  small  importance  whether  the  fuel  burned  be  solid  or 
liquid.     The  only  assumption  is  that  it  is  desirable  to  burn  the 
fuel  as  completely  as  possible  without  the  introduction  of  any 
unnecessary  excess  of  air.     When  gaseous  fuels  are  burned  the 
same    general  principles   apply  but  there  is  somewhat  greater 
complication  in  calculation.     This  chapter  therefore  limits  itself 
to   a  study  of  the  gases  arising  from  complete  combustion  of 
solid  or  liquid  fuels.     Let  us  see  how  much  light  a  knowledge  of 
the  composition  of  the  gas  can  throw  on  the  operation  of  the 
furnace. 

2.  Formation    of    Carbon    Dioxide. — Air     is     composed     of 
practically  21  volumes  of  oxygen  and  79  volumes  of  nitrogen  and 
other  inert  gases.     When  oxygen  unites  with  carbon  there  is 
formed  carbon  dioxide  which  is  stable  unless  it  comes  into  inti- 
mate contact  with  carbon  or  other  reducing  agent  at  a  high  tem- 
perature.    Chemically  the  result  is  expressed  as  follows: 

C  +  02  =  C02. 

The  expression  means  not  only  that  carbon  dioxide  is  formed 
by  the  union  of  carbon  and  oxygen,  but  also  indicates  that  one 
volume  of  carbon  dioxide  is  formed  from  one  volume  of  oxygen  and 
that  the  volume  of  the  smoke  gases  after  cooling  is  the  same  as  that 
of  the  air  which  was  used.  This  follows  from  the  law  of  Gay 
Lussac  which  states  that  a  molecule  of  one  gas  occupies  the  same 
volume  as  that  of  any  other  gas  under  like  conditions.  The 
simplicity  of  this  volume  relation  makes  it  extremely  desirable 
to  work  with  volumes  instead  of  weights  in  problems  where  gases 
are  involved. 

139 


140  GAS  AND  FUEL  ANALYSIS 

Since  one  volume  of  oxygen  forms  one  volume  of  carbon  dioxide 
it  follows  that  the  theoretical  best  composition  of  the  chimney 
gases  from  the  combustion  of  carbon  would  be  21  per  cent.  CO2 
and  79  per  cent.  N2.  This  is  unattainable  in  practice  because  the 
strong  reducing  action  of  the  glowing  carbon  on  the  carbon 
dioxide  will  cause  formation  of  carbon  monoxide  (CO)  which  will 
not  be  again  oxidized  unless  it  is  brought  in  contact  with  free 
oxygen  while  still  at  a  high  temperature.  An  excess  of  oxygen  is 
in  practice  necessary  to  ensure  this.  It  follows  from  the  fact  that 
the  volume  of  the  carbon  dioxide  is  the  same  as  that  of  the  oxygen 
which  formed  it,  that  all  chimney  gases  resulting  from  the  combus- 
tion of  pure  carbon  to  carbon  dioxide  will  contain  21  per  cent,  of 
C02+02  and  79  per  cent,  of  N2. 

3.  Effect  of  Hydrogen  of  Coal  on  Composition  of  Chimney 
Gases. — The  simple  relation  stated  in  the  preceding  section  only 
holds  where  carbon  is  the  only  fuel  burned,  a  condition  which  is 
quite  closely  fulfilled  with  a  coke  fire  and  approximately  ful- 
filled when  anthracite  coal  is  the  fuel.  When  fuels  contain  not- 
able percentages  of  hydrogen  as  does  bituminous  coal,  and  to  a 
greater  extent  petroleum  and  most  gaseous  fuels,  part  of  the 
oxygen  of  the  air  burns  to  water  which  escapes  from  the  furnace 
as  steam.  When  the  gas  is  sampled  for  analysis  part  of  this  steam 
may  condense.  When  the  gas  sample  is  stored  over  water  it 
becomes  fully  saturated  with  water  vapor  so  that  its  volume  is  in- 
dependent of  the  amount  of  steam  which  it  contained  in  the  chim- 
ney and  the  result  is  the  same  as  if  the  steam  formed  in  combustion 
had  all  condensed  and  the  gas  had  later  become  saturated  with 
water  vapor  as  happens,  for  instance,  in  the  gas  analysis  appa- 
ratus. This  is  the  assumption  which  is  made  in  discussing 
combustion. 

If,  then,  part  of  the  oxygen  of  the  air  combines  with  hydrogen 
of  the  fuel  to  form  steam  which  condenses  to  a  liquid  while  the 
nitrogen  associated  with  this  oxygen  remains  as  a  gas,  it  is  apparent 
that  the  percentage  of  nitrogen  in  the  chimney  gas  must  be  more 
than  the  79  per  cent,  present  in  the  air.  The  extent  of  the  change 
of  volume  may  be  readily  calculated.  Assume  that  an  analysis 
shows  81  per  cent.  N2.  100  cu.  ft.  of  air  contained  79  cu.  ft.  of 
nitrogen,  which  is  now  81  per  cent,  of  the  chimney  gas,  therefore 

79 
the  volume  of  the  gas  is  ^r-^.  =  0.975  or  97.5  per  cent,  of  the  initial 

U.  ol 


CHIM.NEY  GASES  141 

volume  of  air  measured  under  the  same  condition  of  temperature 
and  pressure.  It  follows  that  2.5  of  the  21  volumes  of  oxygen 
in  100  air  have  combined  with  hydrogen  to  form  water. 

The  volume  of  the  water  formed,  so  long  as  it  remains  in  the 
vapor  form,  will  be  twice  that  of  the  oxygen  from  which  it  was 
formed  as  shown  by  the  equation 

2H2+O2  =  2H2O. 

The  hydrogen  in  this  case  is  contained  in  the  coal  and  is  considered 
as  a  solid  just  as  the  carbon  is.  In  the  case  of  gaseous  fuels  the 
problem  is  a  little  more  complicated  and  is  treated  under  Pro- 
ducer Gas. 

4.  Carbon  Monoxide  and  Products  of  Incomplete  Combus- 
tion.— The  presence  of  carbon  monoxide,  hydrogen  or  hydro- 
carbons is  a  sign  of  incomplete  combustion  and  represents 
loss  of  heat  which  would  have  been  liberated  in  the  furnace  had 
combustion  been  complete. 

Heating  value  1  Ib.  C  to  CO2 14,600  B.t.u. 

1  Ib.  C  to  CO 4,450  B.t.u. 

Since  carbon  burning  to  CO  only  evolves  30  per  cent,  of  the  heat 
obtainable  by  complete  combustion  it  is  evidently  uneconomical 
to  allow  more  than  small  amounts  of  this  gas  to  appear  in  chimney 
gases. 

It  is  frequently  stated  that  carbon  monoxide  is  formed  when 
carbon  burns  with  an  insufficient  supply  of  air.  This  is  only  a 
partial  truth  for  with  a  bed  of  coals  at  a  dull  red  heat  it  is  difficult 
to  form  carbon  monoxide  no  matter  how  much  the  air  supply  is 
limited.  If  the  free  oxygen  in  the  chimney  gases  is  below  3 
per  cent,  it  will  be  entirely  normal  to  find  products  of  incomplete 
combustion.  The  presence  of  carbon  monoxide  and  other  in- 
completely burned  gases  is  abnormal  when  associated  with  much 
more  than  3  per  cent,  free  oxygen.  It  indicates  either  a  faulty 
design  of  the  furnace  or  carelessness  on  the  part  of  the  fireman. 
Furnaces  intended  for  coal  high  in  volatile  matter  must  have 
roomy  combustion  chambers  so  that  the  streams  of  gas  given  off 
by  the  coal  may  have  time  to  mix  with  air  and  burn  before  they 
become  chilled  by  contact  with  cold  surfaces.  Furnaces  designed 
for  anthracite  coal  do  not  have  such  large  combustion  chambers 
and  hence  do  not  give  good  results  with  bituminous  coal. 


142  GAS  AND  FUEL  ANALYSIS 

As  mentioned  in  Chapter  III,  the  estimation  of  carbon  monoxide 
presents  some  difficulties  and  the  careless  analyst  may  readily 
report  a  fraction  of  a  per  cent,  of  carbon  monoxide  when  none  is 
there.  On  the  other  hand,  the  natural  tendency  is  to  fail  to  find 
hydrogen  when  it  is  present  in  only  small  amounts. 

The  presence  of  soot  in  chimney  gases  is  not  necessarily  an  in- 
dication that  measureable  amounts  of  unburned  gases  are  present 
for  the  particles  of  tar  and  carbon  formed  by  the  destructive 
distillation  of  the  coal  burn  much  more  slowly  than  do  the 
gases  and  also  have  higher  ignition  temperatures  and  so  are  more 
likely  to  escape  combustion. 

5.  Volume  of  Air  and  of  Chimney  Gases. — The  volume  of  the 
air  used  in  combustion  per  pound  of  carbon  and  the  volume  of  the 
chimney  gases  may  be  calculated  from  the  gas  analysis.  The 
method  is  based  on  the  assumption  that  the  nitrogen  of  the  air 
passes  through  the  furnace  unchanged  in  volume,  and  that  all  of 
the  nitrogen  of  the  chimney  gases  is  derived  from  the  air.  This 
assumption  is  practically  correct,  the  small  amount  of  nitrogen 
derived  from  the  coal  introducing  only  a  negligible  error. 

It  is  necessary  also  to  have  some  factor  to  connect  the  weight 
of  carbon  burned  with  the  volume  of  the  chimney  gases.  One 
pound  of  carbon  burning  to  C02  requires  32.1  cu.  ft.  of  oxygen 
measured  wet  at  60°  F.  and  30  in.  barometric  pressure  and 
yields  32.1  cu.  ft.  carbon  dioxide. 

Let  us  assume  the  following  gas  analysis : 

CO2 8.5  per  cent. 

O2 9. 8  per  cent. 

N2 81.7  per  cent. 

It  was  shown  in  §  3  that  the  increase  in  the  percentage  of  the 
nitrogen  over  79  was  due  to  the  condensation  of  steam  formed  by 
the  union  of  hydrogen  of  the  coal  with  oxygen  of  the  air.  The 
volume  of  these  gases  referred  to  100  of  air  may  be  obtained  by 

79 
multiplying  them  by  the  factor  CJT^,  —  0.966. 

8.5X0.966=   8.2CO2 

9.8X0.966=  9.5     O2 

81.7X0.966  =  78.^    N2 

96.5 

Oa  which  has  disappeared  as  steam    3 . 5   forming  7 . 0  steam. 

100.0    ' 


CHIMNEY  GASES  143 

The  volume  of  air  used  per  pound  of  carbon  may  now  be  ob- 
tained. 

To  burn  1  Ib.  carbon  =32.  \  cu.  ft.  O2  forming  32. 1  cu.  ft.  COa 

32.1X9.5 
Oxygen  in  excess  — g-= —       =  37 . 2 

Oxygen  forming  steam  — '     ~        =13.7 

Total  oxygen  per  pound  carbon,        83.0  cu.  ft. 

79 
Accompanied  by  21  X  83.0  =312.0  cu.  ft.  N2 

Corresponding  to  395 . 0  cu.  ft.  air. 

The  excess  of  air  may  be  determined  from  the  ratio 

Oxygen  used        32.1+37.2+13.7     83.0 
Oxygen  required"       32.1+13.7  ~    ~45.8 

The  volume  of  the  chimney  gases  is  obtained  directly  from  the 
above,  it  being  remembered  that  the  volume  of  the  CC>2  is  the 
same  as  that  of  the  O%  forming  it  and  that  the  volume  of -the  steam 
(assumed  to  be  cooled  to  standard  temperature  without  condensa- 
tion) is  twice  the  volume  of  the  oxygen  forming  it. 

Volume  of  chimney  gases  from  1  Ib.  carbon  in  the  above 
example : 

CO2 32 . 1  cu.  ft. 

H2O  vapor  2X13.7 27.4  cu.  ft. 

O2 37.2  cu.  ft. 

N2 312. Ocu.  ft. 

Total  chimney  gases  408.7  cu.  ft. 

6.  Loss  of  Heat  in  Chimney  Gases. — The  heat  carried  away 
by  these  gases  may  be  determined  by  multiplying  their  volume  by 
the  rise  in  temperature  and  by  their  specific  heat.  It  was  first 
shown  in  1883  by  Mallard  and  LeChatelier  that  the  specific  heats 
of  gases  are  not  constant  but  increase  with  rising  temperature. 
Engineers  have  been  slow  to  adopt  these  variable  specific  heats 
but  there  can  be  no  question  as  to  their  general  correctness.  The 
mean  specific  heats  expressed  in  British  thermal  units  per  cubic 
foot  and  per  pound  at  constant  pressure  have  been  calculated  by 
the  author  from  the  most  recent  data  of  Holborn  and  Henning1 

*  Annalen  der  Physik,  23,  809  (1907). 


144  GAS  AND  FUEL  ANALYSIS 

and  are  given  in  Tables  V  and  VI  of  the  Appendix.  It  will  be 
noted  that  the  specific  heats  of  oxygen,  nitrogen  and  all  permanent 
gases  are  the  same  per  cubic  foot,  an  agreement  which  holds  true 
only  for  specific  heats  by  volume  and  not  for  those  for  which  the 
unit  basis  is  weight. 

The  loss  of  heat  per  pound  of  carbon  in  the  particular  case 
given  above  will  be  calculated  as  follows,  a  temperature  of  600° 
F.  for  the  escaping  gases  being  assumed: 

Temperature  through  which  gases  are  heated  600  —  60=540. 

Use  mean  specific  heats  from  Table  V  corresponding  to  600°  F. 
/ 

Heat  lost  in  CO2,  32 . 1  XO . 0253  X540  =  439  B.t.u. 

Heat  lost  in  steam,        27 . 4 XO . 0221  X540  =  328 

Heat  lost  in  oxygen,      37.2  \  349.2x0.oi77X540  =3340  B.t.u. 
Heat  lost  in  nitrogen,  312      J 

4107 

It  is  necessary  to  know  the  percentage  of  carbon  in  the  coal 
before  this  loss  of  heat  per  pound  carbon  can  be  calculated  to 
the  desired  basis  of  loss  per  pound  of  coal. 
The  loss  of  heat  per  pound  of  dry  coal  = 

Loss  per  pound  carbon  X  per  cent,  carbon  in  dry  coalt 
"100 

Moisture  present  in  the  coal  when  placed  on  the  fire  will  be 
vaporized,  and,  in  case  combustion  is  complete,  will  escape  from 
the  stack  as  steam.  It  is  immaterial  whether  or  not  it  underwent 
decomposition  in  the  fire,  only  the  initial  and  final  states  being 
important.  The  amount  of  water  thus  vaporized  calculated 
from  the  analysis  of  the  coal  is  reported  in  pounds  and  is  most 
conveniently  kept  in  that  form  throughout  the  calculation.  The 
mean  specific  heats  by  weight  at  constant  pressure  are  given  in 
Table  VI  of  the  Appendix.  Moisture  present  in  the  air  intro- 
duced into  the  firebox  will  be  heated  from  room  temperature  to 
that  of  the  escaping  gases.  Its  amount  may  be  determined  from 
observations  with  a  wet  and  dry  bulb  thermometer  from  which  the 
percentage  humidity  may  be  calculated  as  described  in  §  14  of 
Chapter  VII.  The  volume  of  water  vapor  per  cubic  foot  of  air 
for  various  temperatures  is  given  in  Table  VII  of  the  Appendix. 

There  is  also  steam  in  the  stack  gases  which  is  derived  from 
the  union  of  the  hydrogen  and  oxygen  of  the  coal  with  each 
other.  It  is  sufficiently  accurate  to  assume  that  all  of  the  oxy- 


CHIMNEY  GASES 


145 


gen  of  the  coal  unites  with  the  hydrogen  of  the  coal  to  form  water, 
that  the  excess  or  available  hydrogen  unites  with  the  oxygen  of 
the  air  to  form  water  and  that  all  of  the  carbon  of  the  coal 
unites  with  the  oxygen  of  the  air  'to  form  carbon  dioxide.  The 
volume  of  steam  due  to  this  union  of  the  hydrogen  and  oxygen 
of  the  coal  with  each  other  can  only  be  accurately  calculated  from 
an  ultimate  analysis.  Fortunately  its  amount  is  small  and  fairly 
constant  for  a  given  type  of  coal.  The  weight  of  water  so  formed, 
sometimes  called  " combined  water,"  may  be  taken  as: 


2.5  per  cent  for  anthracite  coals. 

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146  GAS  AND  FUEL  ANALYSIS 

Volume  chimney  gases  from  1  Ib.  carbon. 

OO       1 

1  Ib.  carbon  produces  32.1  cu.  ft.  CO2.     Factor  -pr-^  =3.45 

9 .  o 

9.3X3.45=  32.1  cu.  ft.  CO2 

6.0X3.45=  20.7  cu.  ft.  H2O  vapor 
8.7X3.45=  30.0cu.  ft.     O2 
79.0X3.45=272.2  cu.  ft.     N2 


Volume  air  required  for  combustion  100X3.45=345  cu.  ft. 
Moisture  in  air  for  combustion: 


75  per  cent,  of  saturation  at  70°  =0.75X0. 026  =0.019  cu.  ft.  per 

cubic  foot  air. 
345X0.019  =  6.56  cu.  ft.  H2O  vapor  in  air  for  1  Ib.  carbon. 

Gases  heated  from  70° -720°  =  650°  F. 

Loss  in  CO2       =32.1X650X0.0253  =529 

LossinH2O      =20.7+6.6=27.3X650X0.0221  =  392 

Loss  in  O2+N2  =  30. 0+272. 2=302. 2X650X0. 0177  =3440 

B.t.u.  lost  in  gases  per  Ib.  carbon  burned  =4361 

B.t.u.  lost  in  gases  per  Ib.  coal  burned  4361  X 0.0716  =3122 

Moisture  in  coal  9.3  per  cent  =0.093  Ibs.    per  Ib.  coal. 

Combined  water  in  coal  6.0  per  cent        =0.060  Ibs.    per  Ib.  coal. 
Total  water  with  coal  =0. 153  Ibs.    per  Ib.  coal. 

Heat  absorbed  in  converting  1  Ib.  water 

to  vapor  at  70°  F.  =  1067.  B.t.u. 
Heat  absorbed  in  converting  0. 153  Ibs. 

water  to  vapor  at  70°  F.  =0.153 

X1067.  =   163.  B.t.u. 

Heat  absorbed   in   raising  0.153   Ibs. 

water    vapor    from    70°  —  720°  = 

0.153X650.  X  0.4673  =     46.  B.t.u. 

Total  heat  lost  in  water  with  coal  =  209.  B.t.u. 

Heat  lost  in  gases  per  Ib.  coal  =3122.  B.t.u. 

Heat  lost  in  water  per  Ib.  coal  =  209.  B.t.u. 

Total  heat  lost  per  Ib.  coal  burned  =3331.  B.t.u. 

3331 
Per  cent,  heat  lost  =  v^-rr^=26,7  per  cent. 


CHIMNEY  GASES  147 

7.  Interpretation  of  Analysis  of  Chimney  Gases. — The  con- 
clusions indicated  in  the  preceding  paragraphs  may  be  summar- 
ized as  follows: 

Carbon  Dioxide. — The  higher  the  percentage  of  C02  in  chimney 
gases  without  the  presence  of  CO  or  hydrocarbons,  the  more 
efficient  is  the  furnace.  When  the  fuel  is  coke  or  anthracite  coal 
the  sum  of  the  percentages  of  carbon  dioxide  and  oxygen  should  be 
between  20.5  and  20.8.  If  the  fuel  is  bituminous  coal  the  sum  of 
the  carbon  dioxide  and  oxygen  will  drop  to  19  per  cent,  and  if  the 
fuel  is  oil  or  gas  the  figure  will  be  still  smaller.  In  ordinary  prac- 
tice the  percentage  of  carbon  dioxide  should  be  as  large  as  the 
oxygen,  and  with  well-equipped  and  operated  plants  the  pro- 
portion of  CO-2  to  62  should  be  as  high  as  2  to  1.  With  liquid  or 
gaseous  fuels  the  proportion  of  CO2  will  be  still  higher. 

The  C02  as  reported  includes  a  small  amount  of  SO2  from  the 
sulphur  of  the  coal,  which  does  not  usually  amount  to  more  than 
a  few  hundredths  of  a  per  cent. 

Oxygen. — When  solid  fuel  is  burned  on  an  ordinary  grate  it  is 
necessary  to  have  an  excess  of  air  to  insure  complete  combustion. 
This  excess  should  be  kept  as  small  as  possible. 

Carbon  Monoxide  and  Products  of  Incomplete  Combustion. — 
These  products  should  be  entirely  absent  from  chimney  gases. 
Their  presence  indicates  waste  of  fuel.  Unless  the  analytical 
work  is  carefully  done  as  much  as  0.2  per  cent.  CO  may  readily  be 
reported  through  error. 

Nitrogen. — Nitrogen  is  present  in  air  to  the  extent  of  79  per 
cent,  by  volume  and  will  be  present  in  at  least  that  percentage  in 
chimney  gases.  With  bituminous  coal  the  percentage  will  rise 
to  81  per  cent,  and  with  oil  or  gaseous  fuel  the  percentage  will 
be  higher.  The  percentage  of  nitrogen  can  only  fall  below  79 
per  cent,  through  the  introduction  of  some  gas  which  makes  the 
total  volume  of  the  chimney  gases  greater  than  that  of  the  air  from 
which  they  were  derived.  The  formation  of  carbon  monoxide 
will  affect  this  result  since  it  occupies  twice  as  much  space  as 
the  oxygen  from  which  it  was  derived.  The  amount  of  CO  in 
chimney  gases  is,  however,  too  small  to  exert  any  appreciable 
influence  of  this  sort. 

Loss  of  Heat  in  Chimney  Gases. — The  loss  of  heat  will  depend 
on  the  temperature  and  volume  of  the  gases.  The  volume  of  the 


148  GAS  AND  FUEL  ANALYSIS 

gas  is  in  general  indicated  by  the  relative  percentage  of  carbon 
dioxide  and  oxygen.  The  higher  the  per  cent,  of  oxygen  and  the 
lower  the  per  cent,  of  carbon  dioxide  the  greater  is  the  loss  of  heat. 
The  loss  will  vary  in  steam-boiler  practice  between  15  and  45 
per  cent.  With  smelting  furnaces  where  the  gases  escape  at 
high  temperatures  the  loss  may  be  much  higher. 


CHAPTER  XI 


PRODUCER  GAS 

1.  Formation    of    Producer    Gas. — Producer    gas    is    formed 
whenever  air  is  brought  into  contact  with  fuel  under  such  con- 

Constituent  of  the 

formation  of  pro- 
i\  lete  (iombustion, 
i :  .ited  cmantity  of 

h   -e  carbon  monox- 
LS  in  air 


ai|t  with  glowing 
jo  11   monoxide  is 


and  the 


converted 


150 


GAS  AND  FUEL  ANALYSIS 


If  the  temperature  of  the  producer  is  low,  this  reaction  may 
proceed  in  part  as  follows: 

C  +  2H2O  =  CO2+2H2. 

If  bituminous  coal  is  placed  in  the  producer  there  will  also  be 
products  of  destructive  distillation  including  hydrocarbons  both 
saturated  and  unsaturated,  hydrogen  and  carbon  monoxide. 

The  largest  single  constituent  of  producer  gas  is  nitrogen,  which 
will  not  often  fall  below  50  per  cent.  Carbon  monoxide  and 
hydrogen  rank  next  in  'percentage.  The  hydrocarbons  are 
practically  always  under  5  and  are  usually  less  than  3  per 
cent.  Carbon  dioxide  should  be  low.  It  is,  however,  frequently 
as  high  as  10  per  cent. 

The  following  are  some  typical  analyses  of  producer  gas.1 

TYPICAL  ANALYSES  OF  UP-DRAFT  PRESSURE-PRODUCER  GAS 

(Per  cent,  by  volume) 


From 
Bituminous  Coal 

From 
Lignite 

From 
Peat 

Carbon  dioxide  (CO2)  

9  84 

10  55 

12.40 

Oxygen  (O2) 

04 

0  16 

0  00 

Ethylene  (C2H4)   

.18 

0.17 

0.04 

Carbon  Monoxide  (CO) 

18  28 

18  72 

21.00 

Hydrogen  (H2) 

12  90 

13  74 

18  50 

Methane  (CH4)  

3.12 

3.44 

2.20 

Nitrogen  (N2)  .  . 

55.64 

53.22 

45.50 

TYPICAL  ANALYSES  OF  DOWN-DRAFT  PRODUCER  GAS 
(Per  cent,  by  volume) 


From 
Bituminous  Coal 

From 
Lignite 

From 

Peat 

Carbon  dioxide  (CO2)  
Oxygen  (O2) 

6.22 
0  13 

11.87 
0.01 

10.94 
0.41 

Ethylene  (C2H4) 

0  01 

0.00 

0.06 

Carbon  monoxide  (CO)  

21.05 

16.01 

16.91 

Hydrogen  (H2)  

12  01 

14.76 

10.19 

Methane  (CH4) 

0  49 

0.98 

0.66 

Nitroeen  (No)  .  . 

60.09 

56.37 

60.83 

1  From  Bulletin   13,  U.  S.  Bureau  of  Mines.     "Resum6  of  Producer-Gas 
Investigations  by  R.  H.  Fernald  and  C.  D.  Smith. 


PRODUCER  GAS  151 

2.  Sampling    Producer    Gas. — The    quality    of    gas    yielded 
by  a  given  producer  may  change  quickly.     Soon  after  a  charge 
of  bituminous  coal  has  been  addec},  the  amount  of  volatile  tarry 
vapors  and  of  gaseous  hydrocarbons  in  the  gas  increases.     Within 
a  half  hour  the  larger  part  of  the  volatile  matters  may  have  dis- 
tilled off  leaving  the  gas  almost  free  from  hydrocarbons  and  from 
tar  vapors.     Rapid  changes  will  also  be  noted  after  poking  the 
fire. 

An  average  sample  of  producer  gas  may  be  obtained  only 
by  extending  the  sampling  over  a  long  period,  as  directed  in 
Chapter  I.  There  will  be  especial  difficulty  in  determining  the 
quantity  and  heat  value  of  the  suspended  tarry  particles.  Yet 
these  values  must  be  ascertained  if  the  heat  value  of  the  crude 
gas  is  to  be  determined  accurately.  The  method  of  collecting 
the  tar  particles  on  filter  papers,  given  in  Chapter  IX,  may  be 
followed  and  the  weight  of  tar  per  cubic  foot  of  gas  thus  obtained. 
The  papers  and  tar  may  then  be  burned  in  a  bomb  calorimeter 
and  after  deduction  of  the  heat  due  to  the  known  amount  of 
filter  paper,  the  heating  value  of  the  tar  may  be  obtained.  This 
determination  is  not  often  made,  as  it  is  difficult  to  carry  it  out 
accurately.  However,  it  is  not  possible  to  find  the  true  heat 
balance  on  a  furnace  fired  with  crude  producer  gas,  especially  if 
from  a  bituminous  producer,  unless  such  a  determination  is  made. 

Ordinarily  the  determination  of  tar  and  suspended  particles 
is  neglected  and  the  sampling  then  is  to  be  conducted  as  described 
in  Chapter  I. 

3.  Analysis    of    Producer    Gas. — The     constituents    to     be 
determined  in  producer  gas  are   carbon  dioxide,   unsaturated 
hydrocarbons,  oxygen,  carbon  monoxide,  hydrogen  and  methane. 
The  methods  are  given  in  Chapters  II,  III  and  IV.     No  difficulty 
will  be  experienced  except  with  hydrogen  and  methane.     The 
percentage  of  these  gases,  except  in  water  gas,  is  usually  so  small 
that  a  sample  after  removal  of  the  absorbable  constituents  is  no 
longer  explosive  when  mixed  with  air.     It  should  be  emphasized 
that  failure  to  obtain  an  explosion  does  not  mean  the  absence 
of  hydrogen  and  methane  but  merely  that  they  are  present  in 
less  than  explosive  amounts.     Explosion  may  be  brought  about 
by  addition  of  a  known  volume  of  pure  hydrogen  to  form  an 
explosive  mixture  but  it  is  usually  simpler  to  use  a  method  which 


152  GAS  AND  FUEL  ANALYSIS 

does  not  involve  explosion.  Combustion  with  a  hot  platinum 
spiral  as  in  the  Dennis  and  Hopkins  method  (§  9  of  Chapter  IV) 
or  with  copper  oxide  as  in  the  Jaeger  method  (§  11  of  Chapter 
IV)  affords  a  satisfactory  method  for  determination  of  these 
constituents. 

4.  Interpretation  of  Analysis. — The  important  constituents 
are  carbon  dioxide  and  carbon  monoxide.  Oxygen  should  be 
entirely  absent,  as  it  should  all  have  been  brought  into  combina- 
tion in  its  passage  through  the  producer.  Its  presence  in  a  pro- 
ducer gas  may  be  an  indication  of  leakage  in  sampling  or  of 
leakage  into  the  flue  prior  to  sampling.  Rarely,  if  operating 
conditions  in  the  producer  are  bad,  and  the  fire  is  thin  may, 
there  be  such  a  channel  formed  in  the  producer  that  air  will 
rush  through  the  producer  without  its  oxygen  becoming  combined. 
Such  a  condition  will  be  indicated  by  extremely  high  carbon 
dioxide,  with  low  percentages  of  combustible  gases.  When  a 
producer  is  running  under  normal  conditions  its  operation  may 
be  quite  closely  checked  by  the  percentage  of  carbon  dioxide 
alone.  High  carbon  dioxide  is  in  practically  all  cases  an  un- 
favorable symptom.  It  may  be  due  to  a  cold  fuel  bed  in  the 
producer  caused  either  by  an  excess  of  steam  or  by  slow  running, 
it  may  be  due  to  a  thin  fuel  bed  which  does  not  allow  sufficient 
time  and  contact  for  the  reduction  of  the  carbon  dioxide  to 
monoxide,  and  it  may  be  due  to  channels  or  chimneys  in  a  deep 
fire  which  allow  uncombined  air  to  get  through  the  fuel  bed  and 
burn  above  the  coals. 

A  cold  fuel  bed  in  a  producer  burning  bituminous  coal  will 
tend  to  increase  the  percentage  of  unsaturated  hydrocarbons, 
but  in  no  case  will  they  amount  to  more  than  a  few  tenths  of  a 
per  cent.  A  hot  and  thin  fuel  bed  and  especially  a  channeled 
fuel  bed  will  cause  the  unsaturated  hydrocarbons  to  practically 
disappear,  since  they  are  decomposed  at  the  high  temperature 
and  of  all  the  gases  show  the  greatest  avidity  for  oxygen. 

The  carbon  dioxide  is  almost  a  direct  measure  of  the  thermal 
efficiency  of  the  producer,  the  only  exception  being  its  appear- 
ance as  the  result  of  the  interaction  of  carbon  and  steam  at  a 
relatively  low  temperature  as  in  the  Mond  producer  where  it 
is  accompanied  by  a  high  percentage  of  hydrogen.  Under  other 
circumstances  high  carbon  dioxide  means  low  thermal  efficiency 


PRODUCER  GAS  153 

for  the  70  per  cent,  of  the  energy  of  the  carbon  which  should 
have  been  converted  into  the  potential  energy  of  the  carbon 
monoxide  is  all  changed  to  the  sensible  heat  of  the  carbon 
dioxide  and  accompanying  gases. 

6.  Heating  Value  of  Producer  Gas. — The  heating  value  of 
producer  gas  may  be  determined  in  a  calorimeter  as  described 
in  Chapter  VII  for  illuminating  gas.  A  special  tip  must  be 
used  on  the  burner  and  care  be  taken  to  see  that  the  flame 
burns  clear.  The  heating  value  of  producer  gas  may  be  as 
low  as  100  British  thermal  units  per  cubic  foot  and  it  frequently 
happens  that  it  does  not  burn  readily  in  a  Bunsen  burner. 
The  gas  must  be  carefully  cooled  and  cleaned  before  testing. 
This  operation  separates  tar  whose  amount  and  heat  value  must 
be  determined  as  directed  in  §  2  of  this  chapter.  The  heating 
value  of  the  purified  gas  may  also  be  calculated  from  the 
analysis  as  indicated  in  §  17  of  Chapter  VII.  The  low  per- 
centage of  unsaturated  hydrocarbons  in  producer  gas  makes 
the  errors  of  calculation  less  than  is  the  case  with  illuminating 
gas.  On  account  of  the  difficulty  in  cleaning  the  gas  and  in 
keeping  a  steady  flame  in  the  calorimeter,  the  heating  value  is 
usually  obtained  by  calculation. 

It  is  worth  while  to  emphasize  again  that  the  heating  value 
of  the  cleaned  gas  from  bituminous  coal  is  lower  than  that  of 
the  hot  gas  which  still  contains  tar  vapors  and  that  allowance 
must  be  made  for  the  tar  vapors  in  calculating  the  heat  value  of 
the  gas  which  is  used  while  hot. 

6.  Volume  of  Producer  Gas. — It  would  be  very  desirable  to 
be  able  to  calculate  the  volume  of  producer  gas  per  pound  of 
coal,  as  is  done  in  Chapter  X  for  chimney  gases.  There  are,  how- 
ever, so  many  possible  reactions  in  the  gas  producer  and  the 
changes  in  volume  are  so  complicated,  especially  in  a  bituminous 
producer,  that  it  is  only  possible  to  make  such  calculations  for 
simple  cases. 

Assume  a  producer  burning  pure  carbon  in  dry  air.  It  is 
manifest  that  the  only  products  of  combustion  will  be  C02,CO 
and  N2  Assume  the  following  composition  of  the  gas 

CO2 5.5  per  cent. 

CO 25 . 6  per  cent. 

N2 68.9  per  cent. 


154  GAS  AND  FUEL  ANALYSIS 

The  air  entering  the  producer  was  composed  of  79  volumes 
of  nitrogen  for  every  21  volumes  of  oxygen.  The  change  in 
percentage  of  the  nitrogen  in  the  producer  gas  is  due  to  changes 
resulting  from  the  union  of  oxygen  with  carbon.  The  first  step 
is  to  trace  the  changes  taking  place  when  100  volumes  of  air  pass 
through  the  producer  and  find  the  relative  volumes  of  C02  and 
CO  for  79  volumes  of  N2. 

CO2    5-5><=  6-3=  6.3vols.  O2 


7Q 
N2  68. 9X^^=79. 0  =  79. Ovols.  N2 


•68.9 


100 . 0  vols.  air. 


One  pound  of  carbon  burning  to  carbon  dioxide  requires  32.1 
cu.  ft.  of  oxygen  (at  60°  F.  and  30  in.  of  mercury  pressure)  and 
yields  32. 1  cu.  ft.  of  carbon  dioxide.  One  pound  of  carbon  burning 
to  carbon  monoxide  requires  16.05  cu.  ft.  of  oxygen  and  yields 
32.1  cu.  ft.  of  carbon  monoxide.  It  follows  that  the  weights  of 
carbon  burning  to  CO  and  CO2  are  proportional  to  the  volumes 
of  the  two  gases.  In  the  present  instance 

CO2    6.3=g|-|xiOO  =  17.7percent. 

OQ  4 
CO   29. 4  =  ^^X100  =  82. 3  per  cent. 

oO .  i 

35.7 
One  pound  of  carbon  yields 

0.177X32.1=     5.7cu.  ft.  CO2 
0.823X32.1=  26.4cu.  ft.  CO 
3.76   X 32. 1  =  120. 7  cu.  ft.     N2 

152.8  cu.  ft.  producer  gas.* 

The  sensible  heat  will  be  calculated  as  in  Chapter  X. 

5.7X0268X1000=   153  B.  t.  u. 
26.4 
120.7 

147.1X0180X1000  =  2647  B.  t.  u. 
2800  B.  t.  u. 


PRODUCER  GAS  155 

Energy  in  26.4  cu.  ft.  of  CO  8534  B.  t.  u. 

Sensible  heat  in  gases  2800  B.  t.  u. 

Total  energy  in  gas  at  1000°  F.      11334  B.  t.  u. 
Efficiency  of  producer  when  gas  is  used  at 

1000°  F.  =  X100  =  77.6  per  cent. 


7.  Efficiency  of  a  Gas  Producer.  —  In  the  simple  instance  cited 
above  it  is  easy  to  calculate  the  energy  contained  in  the  gas. 
The  only  potential  energy  in  the  gas  from  one  pound  of  carbon 
is  contained  in  the  0.823  lb.,  which  is  now  in  the  form  of  26.4  cu. 
ft.  carbon  monoxide.  The  heating  value  of  this  is: 

26.4X323.5=8534  B.t.u. 

The  total  energy  of  the  coal  if  burned  to  carbon  dioxide  would 
be  14600  British  thermal  units.  If  the  gas  is  cooled  before  being 
burned  so  that  its  only  energy  is  the  potential  energy  of  the  carbon 
monoxide  the  efficiency  of  the  producer  is 

14600  Xl°°  =  58'4  per  Cent> 

If  the  gas  is  burned  while  still  hot,  say  at  1000°  F.,  there  should 
be  credited  to  the  producer  also  the  sensible  heat  of  the  gas,  as 
calculated  in  the  preceding  section  where  the  efficiency  was  shown 
to  be  77.6  per  cent. 

The  above  simple  relations  do  not  hold  when  steam  is  being 
injected  into  the  producer  with  the  air  nor  when  bituminous  coal 
is  being  used  as  a  fuel.  On  account  of  the  varied  possibilities  of 
chemical  reaction  in  these  cases  the  volume  of  the  gases  cannot 
be  calculated  from  their  chemical  composition.  If  the  volume 
of  the  gases  is  measured  by  a  Venturi  meter,  or  otherwise,  then  it 
is  possible  to  calculate  the  sensible  and  potential  energy  of  the 
gases  as  indicated  in  this  chapter  and  the  one  preceding. 


CHAPTER  XII 
ILLUMINATING  GAS  AND  NATURAL  GAS 

1.  Introduction. — Chemical    analysis    plays  a  minor  role  in 
testing  illuminating  gas  and  natural  gas.     The  determination 
of  heating  value  is  described  in  Chapter  VII  and  of  candle-power 
in  Chapter  VIII.     The  ordinary  chemical  analysis  as  described 
in  Chapters  III  and  IV  usually  includes  the  determination  of 
carbon  dioxide,  unsaturated  hydrocarbons,  oxygen,  carbon  monox- 
ide, hydrogen  and  methane,  nitrogen  being  taken  by  difference.    A 
separate  determination  of  benzene  is  sometimes  desired  in  illu- 
minating gas  and  of  gasoline  vapors  in  natural  gas.     Sulphur 
may  be  called  for  in  both  gases.     Napthalene  and  ammonia  are 
frequently  determined  in  coal  gas. 

2.  Sampling. — The  sampling  of  natural  gas  and  of  purified 
illuminating  gas  usually  offers  little  difficulty,  since  the  gases 
are  thoroughly  mixed  and  contain  such  small  amounts  of  sus- 
pended particles  that  they   are   usually  negligible.     The   chief 
point  to  be  observed  in  sampling  from  service  pipes  in  cities  is  to 
see  that  the  ga's  is  allowed  to  run  long  enough  to  flush  out  the 
pipe  and  bring  to  the  sampling  cock  gas  which  is  representative 
of  that  flowing  in  the  mains.     Illuminating  gas  of  high  candle- 
power  must  not  become  chilled  in  the  sampling  process,  for  there 
is  danger  of  condensing  the  benzene  or  other  hydrocarbon  vapors 
which  it  contains.     Rubber  connections  are  also   to  be  mini- 
mized in  sampling  because  of  the  solubility  of  the  hydrocarbons  in 
rubber.     The  water  used  in  the  sampling  vessels  must  be  carefully 
saturated   before   use,  because   unsaturated   hydrocarbons    are 
relatively  soluble  in  water. 

In  case  unpurified  illuminating  gas  is  to  be  sampled,  additional 
precautions  must  be  taken  an  account  of  the  presence  of  material 
amounts  of  ammonia,  hydrogen  sulphide,  carbon  dioxide  and 
other  very  soluble  gases,  as  well  as  suspended  tar  particles.  In 
case  it  is  sufficient  to  determine  what  the  approximate  composi- 
tion of  the  gas  would  be  after  purification  it  is  sufficiently  accu- 

156 


ILLUMINATING  GAS  AND  NATURAL  GAS  157 

rate  to  sample  in  the  usual  way  and  trust  the  water  of  the  samp- 
ling tank  to  remove  the  ammonia,  hydrogen  sulphide  and  part 
of  the  carbon  dioxide.  In  case  the  actual  composition  of  the 
unpurified  gas  is  desired,  these  soluble  constituents  must  be 
separately  determined  as  indicated  in  succeeding  sections. 

3.  General  Scheme  of  Analysis. — Carbon  dioxide,  unsaturated 
hydrocarbons,  oxygen,  carbon  monoxide,  hydrogen  and  methane 
are  usually  determined  according  to  the  methods  of  Chapters  III 
and  IV.     In  the  case  of  unpurified  illuminating  gas  there  may 
be  appreciable  amounts  of  hydrogen  sulphide  absorbed  with  the 
carbon  dioxide.     If  it  is  desired  to  separate  the  two  the  hydrogen 
sulphide  may  be  estimated  according  to  the  method  of  §  6.    The  es- 
timation of  carbon  dioxide,  oxygen  and  carbon  monoxide  does  not 
present  any  peculiarities,  although  emphasis  should  be  laid  on  the 
necessity  of  complete  removal  of  the  unsaturated  hydrocarbons 
before  the  estimation  of  oxygen  by  phosphorus.     In  the  case  of 
Pintsch  gas  it  sometimes  requires  five  minutes'  shaking  with 
bromine  water  to  affect  such  a  complete  removal  of  the  hydro- 
carbons that  the  phosphorus  will  smoke  when  the  gas  is  sub- 
sequently passed  over  it.     The  determination  of  hydrogen  and 
methane  in  illuminating  gas  offers  no  marked  peculiarity.     In 
natural  gas,  vapors  of  the  gasolines  may  be  present  and  compli- 
cate the  calculation.     Ethane  may  also  be  present  in  natural  gas 
and  also  in  water  gas  and  Pintsch  gas.     The  methods  for  its 
determination  have  been  discussed  in  Chapter  IV.     Nitrogen  is 
taken  by  difference  and  as  the  analysis  is  a  rather  long  and  com- 
plicated one,  the  errors  piling  up  on  the  nitrogen  are  apt  to  be 
material.     A  direct  combustion  of  the  gas  with  copper  oxide,  as 
described  in  §  12  of  Chapter  IV,  gives  a  more  accurate  determina- 
tion of  the  residual  nitrogen. 

4.  Chemical  Composition  of  Illuminating  Gas. — The  so-called 
"coal  gas"  is  made  by  the  destructive  distillation  of  coal  in  closed 
retorts.     The  composition  of  the  gas  is  dependent  on  the  compo- 
sition of  the  coal,  the  temperature  of  the  retort  and  to  some  extent 
its  shape  and  size.     There  is  nothing,  however,  which  distinctly 
characterizes  gas  from  the  large  retort  of  the  by-product  coke 
oven  from  that  of  the  small  horizontal  retort  of  the  gas  works. 
The  oxygen  of  the  coal  appears  in  the   gas  partly  as  carbon 
dioxide,  partly  as  carbon  monoxide,  and  partly  as  water  vapor. 


158 


GAS  AND  FUEL  ANALYSIS 


None  of  it  will  be  evolved  as  gaseous  oxygen.  The  carbon  monox- 
ide will  be  greater  at  a  high  temperature  than  at  a  low  one,  but 
will  usually  stay  between  the  limits  of  5  and  9  per  cent.  A  high 
retort  temperature  will  cause  cracking  of  the  hydrocarbons  with 
decrease  of  their  percentage  and  increase  of  hydrogen.  A  frac- 
tion of  1  per  cent,  of  free  oxygen  is  normally  present  in  illumin- 
ating gas,  partly  because  of  air  entering  during  the  operation  of 
charging  and  drawing  the  retort,  partly  because, of  leaks  in  the 
long  condensing  system  and  partly  because  of  liberation  of  the 
oxygen  dissolved  in  the  water  used  in  the  scrubbers.  In  so  far 
as  this  oxygen  comes  from  the  air  it  must  be  accompanied  by  four 
volumes  of  nitrogen.  Nitrogen  must  always  be  present  in  this 
amount.  Less  than  four  volumes  of  nitrogen  for  one  of  oxygen 
indicates  a  faulty  analysis.  The  unavoidable  nitrogen  in  the  gas 
arising  from  the  destructive  distillation  of  the  nitrogenous  com- 
pounds of  the  coal  will  be  between  1  and  11/2  per  cent.  High 
percentages  of  nitrogen  unaccompanied  by  a  corresponding 
amount  of  oxygen  indicate  that  suction  has  been  maintained 
on  the  porous  retorts,  so  that  air  has  been  sucked  in.  The 
oxygen  thus  brought  in  contact  with  the  hot  gas  will  at  once  burn 
with  formation  of  carbon  dioxide  or  water  while  the  nitrogen  will 
remain  and  appear  as  such  in  the  purified  gas.  In  the  manufac- 
ture of  water  gas  a  high  percentage  of  nitrogen  will  result  if  the 
gasmaker  turns  the  gas  into  the  holder  before  all  the  gas  pro- 
duced while  blowing  air  is  flushed  from  the  machine  by  the  water 
gas. 

TYPICAL  ANALYSES  OF  ILLUMINATING  GAS 


C6H6  

* 

1.2 

0.2 

* 

1.3 

CO2 

1  5 

1  4 

1  3 

2  7 

3  5 

CnH2n  

4.6 

4.0 

2.0 

6.5 

11.6 

02  
CO  

0.3 
7.1 

0.9 
4.6 

0.5 

4.8 

1.1 
12.4 

0.7 
31.6 

H2  

46.4 

49.6 

50.7 

38.4 

35.7 

CH4  

36.3 

35.0 

38.1 

28.4 

9.0 

N2           .... 

3  7 

3.3 

2  4 

10  5 

3.7 

C2H6  2.9 

'  Not  separately  reported. 


ILLUMINATING  GAS  AND  NATURAL  GAS  159 

1.  Coal  gas  of  17  c.p.  and  650  B.t.u. 

2.  Coke  oven  gas  enriched  by  benzol  to  16.4  c.p.  and  626  B.t.u. 
(Proc.  Am.  Gas  Inst.,  6,  519  (1911).) 

3.  Coke  Oven  Gas.     Fuel  Gas  \Proc.  Am.  Gas  lust.,  6,  519 
(1911).) 

4.  Mixed  Coal  and  Water  Gas  15  c.p.  and  615  B.t.u. 

5.  Carbureted  Water  Gas  of  24  c.p.  and  649  B.t.u.  (Proc.  Am. 
Gaslnst.,7,739  (1912).) 

5.  Benzene. — Benzene  is  a  normal  constituent  of  coal  gas  and 
also  probably  of  water  gas,  but  its  amount  in  unenriched  gases  is 
always  less  than  1  per  cent.,  and  it  is  not  usually  determined. 
Its  solubility  in  water  and  in  caustic  soda  is  slight  so  that  in  the 
ordinary  analysis  the  benzene  is  not  absorbed  by  the  caustic  but 
passes  on  to  the  bromine  pipette  where  it  dissolves  in  the  ethylene 
bromide  formed  in  the  reaction  between  ethylene  and  bromine 
and  is  therefore  estimated  with  the  ethylene  as  "illuminants." 
As  benzene  has  a  very  high  illuminating  power  this  grouping  is 
logical  and  sufficiently  satisfactory  for  most  purposes. 

Hempel  recommends  that  1  c.c.  of  absolute  alcohol  be  placed 
in  a  pipette  otherwise  filled  with  mercury.  An  explosion  pipette 
answers  well  for  this  purpose.  A  sample  of  gas  is  to  be  passed 
into  the  pipette  and  shaken  with  the  alcohol  to  saturate  it  with 
ethylene,  and  the  sample  to  be  analyzed  is  later  passed  into  this 
same  pipette  and  shaken  three  minutes.  The  gas  is  then  drawn 
back  into  the  burette  and  passed  into  a  second  mercury  pipette 
containing  1  c.c.  of  distilled  water  which  removes  the  alcohol 
vapors.  The  decrease  in  volume  from  the  initial  reading  is 
recorded  as  benzene.  The  method  is  to  be  considered  only  an 
approximate  one. 

Morton1  recommends  that,  after  removal  of  carbon  dioxide 
by  caustic  soda  as  usual,  the  gas  be  passed  into  an  ordinary 
simple  absorption  pipette  containing  concentrated  sulphuric 
acid  (sp.  gr.  1.84)  and  shaken  vigorously  for  one  minute.  The 
decrease  in  volume  after  drawing  back  into  the  burette  represents 
benzene.  Dennis  and  McCarthy2  dispute  the  accuracy  of  this 
method  and  propose  ammoniacal  nickel  cyanide  as  a  reagent. 
Their  directions  for  preparation  of  the  reagent  are  as  follows: 

1  Jour.  Am.  Chem.  Soc.,  28,  1728  (1906).  ' 

2  Jour.  Am.  Chem.  Soc.,  30,  233  (1908). 


160  GAS  AND  FUEL  ANALYSIS 

"To  50  grm.  of  nickel  sulphate  (NiS04.7H20),  dissolved  in  75  c.c.  of 
water,  are  added  25  grm.  of  potassium  cyanide  dissolved  in  40  c.c.  of 
water.  After  the  addition  of  125  c.c.  of  ammonium  hydroxide  (sp.  gr. 
0.91)  the  mixture  is  shaken  until  the  nickel  cyanide  has  completely 
dissolved  and  is  then  allowed  to  stand  at  a  temperature  of  0°  for  twenty 
minutes.  The  clear  liquid  is  decanted  from  the  crystals  of  potassium 
sulphate  that  have  been  precipitated,  and  is  treated  with  a  solution 
prepared  by  dissolving  18  grm.  of  crystallized  citric  acid  in  10  c.c.  of 
water.  After  the  mixture  has  stood  again  at  0°  for  ten  minutes,  the 
greenish-blue  supernatant  solution  is  decanted  and  is  introduced  into 
a  gas  pipette.  Two  drops  of  liquid  benzene  are  now  added  to  the  re- 
agent through  the  large  tube  of  the  pipette  and  the  pipette  is  shaken 
until  the  benzene  has  combined  with  the  reagent.  This  is  effected  in 
two  or  three  minutes.  This  addition  of  benzene  to  the  reagent  is  made 
because  it  was  found  that  at  times  a  freshly  prepared  solution  of  the 
ammoniacal  nickel  cyanide  did  not  quantitatively  remove  benzene 
vapor  until  it  had  been  used  for  four  or  five  determinations  and  had 
absorbed  some  of  the  substance." 

The  gas  after  carbon  dioxide  has  been  removed  by  caustic 
is  passed  into  the  pipette  containing  the  ammoniacal  nickel 
cyanide  solution  and  drawn  back  and  forth  between  the  burette 
and  pipette  for  about  two  minutes.  It  is  then  passed  into  a 
five  per  cent,  solution  of  sulphuric  acid  and  shaken  until  the 
ammonia  is  absorbed,  which  requires  about  two  minutes.  Ac- 
cording to  the  authors,  the  absorption  is  quantitative  and  the 
result  unaffected  by  ethylene. 

The  process  of  Haber  and  QEchelhauser1  is  based  on  Bunte's 
observation  of  the  solubility  of  benzene  in  ethylene  bromide. 
The  authors  treat  the  gas  with  a  fresh  solution  of  bromine  water 
to  which  is  added,  immediately  after  the  reaction,  an  excess 
of  strong  potassium  iodide.  The  liberated  iodine  is  titrated 
with  thiosuphate  and  the  difference  between  the  figures  of 
this  titration  and  those  obtained  by  a  blank  test  on  an  equal 
volume  of  the  original  solution  represents  the  bromine  which 
has  combined  with  the  ethylene.  One  cubic  centimeter  deci- 
normal  thiosulphate  corresponds  to  1.12  c.c.  ethylene  at  0°  C. 
and  760  mm.  or  to  1.22  c.c.  at  60°  F.  and  29.5  in.  mercury 
pressure.  The  diminution  in  volume  of  the  gas  after  the  usual 
treatment  with  bromine  water  followed  by  caustic  gives  the 

1  Jour.  JurGaxbd.,  43,  347  (1900). 


ILLUMINATING  GAS  AND  NATURAL  GAS  161 

sum  of  the  benzene  and  ethylene.  The  difference  between  this 
volume  and  that  indicated  by  the  titration  for  ethylene  gives 
the  benzene. 

If  a  more  exact  method  of  estimation  of  benzene  is  desired 
and  a  large  sample  of  gas  can  be  obtained  the  method  of  Harbeck 
and  Lunge1  may  be  used.  It  consists  in  aspirating  10  liters 
of  the  gas  through  a  mixture  of  equal  weights  of  fuming  nitric 
acid  and  concentrated  sulphuric  acid.  Part  of  the  resulting 
dinitrobenzene  crystallizes  out  after  the  acids  are  diluted, 
cooled  and  neutralized,  and  may  be  filtered  and  weighed. 
The  dinitrobenzene  remaining  in  solution  is  extracted  from  an 
aliquot  portion  of  the  filtrate  with  ether  and  also  weighed. 

6.  Hydrogen  Sulphide. — Hydrogen  sulphide  should  be  present 
only  in  minute  traces  in  purified  illuminating  gas.  The  usual 
test  is  an  approximate  one  based  on  the  reaction  of  hydrogen 
sulphide  and  lead  acetate  to  form  black  lead  sulphide.  A 
strip  of  white  filter  paper  moistened  with  colorless  lead  acetate 
is  exposed  to  the  gas  and  the  depth  of  the  resulting  black 
stain  noted.  The  details  of  the  test  differ  widely.  The 
New  York  State  Commission  prescribes  that  gas  shall  show  no 
hydrogen  sulphide  when  tested  by  exposing  the  paper  moistened 
with  lead  acetate  to  a  current  of  gas  burning  at  the  rate  of 
5  cu.  ft.  per  hour.  The  paper  must  not  become  discolored 
after  thirty  seconds  of  such  exposure.  Ramsburg2  has  given 
a  full  discussion  of  the  various  methods  of  testing  for  hydrogen 
sulphide  in  purified  gas. 

Hydrogen  sulphide  is  always  pfesent  in  unpurified  illuminating 
gas.  In  the  ordinary  gas  analysis  it  is  absorbed  by  the  caustic 
soda  simultaneously  with  the  carbon  dioxide  and  reported 
with  it.  Its  quantitative  estimation  may  be  carried  out  as  follows. 
One  or  more  liters  of  the  gas  is  bubbled  through  a  solution 
of  ammoniacal  cadmium  chloride  and  the  resultant  cadmium 
sulphide  is  filtered.  If  the  precipitate  contains  much  tar  it  may 
be  washed  on  the  filter  with  benzol.  Place  filter  and  precipitate 
in  cold  dilute  hydrochloric  acid  till  dissolved  and  titrate  with 
standard  iodine.  If  the  iodine  solution  is  made  by  dissolving 
1.0526  grm.  iodine  to  the  liter,  1  c.c.  will  be  equivalent  to  1/10 

1  Zeit.  fur  anorg.  Chem.,  16,  41  (1898). 
2 Proceedings  Am.  Gas.  Inst.,  4,  453,  1909. 
11 


162  GAS  AND  FUEL  ANALYSIS 

c.c.  of  hydrogen  sulphide  measured  damp  at  60°  F.  and  under 
30  in.  of  mercury  pressure.  A  solution  of  ten  times  the  above 
strength  is  more  convenient  if  much  hydrogen  sulphide  is  present. 

A  rapid  approximate  estimation  of  hydrogen  sulphide  may  be 
made  in  the  Bunte  gas  burette  described  in  §  4  of  Chapter  V. 
The  burette  is  first  filled  with  water  containing  a  little  thin 
starch  paste  to  act  as  indicator,  and  the  sample  of  gas  drawn  in 
and  measured  rapidly  to  prevent  error  due  to  the  solubility  of 
the  hydrogen  sulphide  in  the  water  of  the  burette.  Standard 
iodine  solution  is  now  admitted  from  the  reservoir  at  the  top  of 
the  burette,  about  a  cubic  centimeter  at  a  time,  until  the  blue 
color  formed  by  the  reaction  between  the  iodine  and  starch 
persists  after  repeated  shaking,  showing  that  the  hydrogen  sul- 
phide has  all  been  oxidized.  If  iodine  solution  of  the  concentra- 
tion given  above  has  been  used,  the  volume  of  hydrogen  sulphide 
may  be  read  directly  from  the  volume  of  iodine  used,  which  must 
be  obtained  by  measuring  the  iodine  solution  still  remaining  in 
the  reservoir  of  the  burette.  Tutwiler  has  modified  the  burette 
by  making  the  reservoir  longer  and  graduating  it  so  that  the 
iodine  used  may  be  read  directly. 

7.  Total  Sulphur  Compounds. — Illuminating  gas  and  almost 
all  other  gases  used  for  fuel  contain,  in  addition  to  hydrogen  sul- 
phide, compounds  of  sulphur  and  carbon  such  as  carbon  bisul- 
phide and  more  complex  compounds  like  the  mercaptans.  These 
compounds  are  usually  estimated  after  complete  combustion  in 
which  process  all  the  sulphur,  whatever  its  previous  combination, 
is  converted  into  sulphur  dioxide  and  sulphur  trioxide.  These 
gases  are  absorbed,  oxidized  to  sulphuric  acid  and  weighed  as 
barium  sulphate.  Care  must  be  taken  to  see  that  the  air  used  for 
combustion,  which  is  usually  ten  times  the  volume  of  the  gas, 
is  itself  free  from  sulphur  compounds,  and  that  combustion  is 
complete.  The  form  of  burner  and  absorption  apparatus  is 
immaterial,  except  for  convenience.  The  most  usual  form  is  that 
of  Drehschmidt  which  is  illustrated  in  Fig.  36.  Harding1  and 
Jenkins2  have  both  described  modifications  of  the  apparatus 
which  may  be  made  from  ordinary  laboratory  apparatus  by  any- 
one with  some  skill  in  blowing  glass. 


1  Jour.  Am.  Chem.  Soc.,  28,  537  (1906). 

2  Jour.  Am.  Chem.  Soc.,  28,  542  (1906) 


V 


ILLUMINATING  GAS  AND  NATURAL  GAS 


163 


In  the  Drehschmidt  apparatus  the  gas  is  measured  in  an 
experimental  meter  and  burned  in  a  Bunsen  burner  which  is 
enclosed  in  a  metal  case  and  is  supplied  with  air  which  has  been 
purified  by  passing  through  a  tower  A  in  contact  with  dilute 
caustic  soda.  The  metal  case  surrounding  the  burner  terminates 
at  the  level  of  the  burner  top  and  is  continued  as  a  glass  chimney 
drawn  down  at  the  top  and  terminating  in  a  tube  leading  to  a 
train  of  absorption  bottles.  The  construction  of  the  apparatus 
is  readily  evident  from  the  cut. 

In  making  a  test  about  25  c.  c.  of  dilute  Na2C03  (approximately 


FIG.  36. — Drehschmidt's  sulphur  apparatus. 

5  per  cent.)  is  poured  into  each  of  the  absorption  cylinders  and 
to  the  first  two  are  added  a  drop  or  two  of  bromine  to  oxidize 
the  SO2  vapors.  The  train  is  then  connected  to  an  aspirator. 
The  burner  itself  is  removed  from  the  case,  lighted  and  adjusted 
to  a  consumption  of  about  1  cu.  ft.  of  gas  per  hour.  The  aspira- 
tor is  then  started  and  adjusted  so  that  the  air  bubbles  rapidly 
through  the  absorption  train  and  the  lighted  burner  is  slipped 
into  its  case  where  it  fits  snugly.  If  all  the  adjustments  are 
properly  made  the  gas  continues  to  burn  with  a  clear  blue  flame 
and  the  products  of  combustion  are  sucked  into  the  absorption 
train  where  the  S02  formed  in  combustion  is  absorbed  and  oxi- 


164  GAS  AND  FUEL  ANALYSIS 

dized  to  Na2SC>4.  The  proper  adjustment  of  the  flow  of  air  to 
keep  the  burner  alight  offers  difficulties  to  the  beginner  which 
only  practice  can  overcome.  After  1  cu.  ft.  of  gas  has  been 
burned,  the  burner  is  removed  from  the  casing  and  any  moisture 
which  has  condensed  in  the  glass  chimney  is  rinsed  into  the  car- 
bonate from  the  absorption  vessels.  The  carbonate  is  acidified 
with  HC1,  boiled  and  treated  with  BaCl2  in  the  usual  manner  to 
precipitate  the  sulphate.  1  grm.  BaSO4  =  0.1373  grm.  S.  or  2.119 
grains  S.  The  result  is  usually  reported  as  grains  sulphur  per 
100  cu.  ft.  of  gas  measured  under  standard  conditions. 

8.  Napthalene. — The  amount  of  the  hydrocarbon,  napthalene 
Cio  H8,  usually  present  in  gas  is  less  than  one-tenth  of  1  per  cent. 
Its  small  amount  would  make  it  unworthy  of  consideration 
were  it  not  for  its  disagreeable  property  of  causing  stoppages  in 
gas  mains.  Its  estimation  is  therefore  sometimes  demanded  as 
one  of  the  steps  in  controlling  the  manufacturing  process. 

The  usual  method  for  purified  gas  is  that  devised  by  Coleman 
and  Smith1,  who  based  their  method  on  Kuster's2  method  for 
separating  napthalene  from  other  hydrocarbons.  The  method 
depends  upon  the  property  which  napthalene  possesses  of  combin- 
ing molecule  for  molecule  with  picric  acid  to  form  an  insoluble 
compound.  In  the  author's  laboratory  it  has  been  customary 
to  make  the  picric  acid  about  1/20  normal,  which  is  an  almost 
saturated  solution,  and  to  use  as  alkali  Ba(OH)2  1/5  normal, 
with  phenolphthalein  or  lacmoid  as  indicator.  The  color  change 
is  not  difficult  to  observe,  but  the  same  conditions  must  always 
be  observed  in  the  analysis  that  are  maintained  in  the  standardiza- 
tion. When  the  gas  to  be  tested  has  been  purified  and  there  is 
no  danger  of  napthalene  deposition  at  room  temperature  the  gas 
may  be  passed  through  a  wet  experimental  meter,  then  through 
a  wash  bottle  containing  dilute  tartaric  or  other  non-volatile 
acid  to  remove  all  traces  of  ammonia,  then  through  a  bottle  con- 
taining water  to  stop  acid  which  might  have  spattered  over  and 
then  through  a  bulbed  gas  washing  tube  with  about  ten  bulbs 
containing  50  c.c.  of  the  standard  picric  acid.  A  yellow  precipi- 
tate betrays  the  presence  of  napthalene.  After  five  or  more 
cubic  feet  of  gas  have  been  bubbled  through  the  apparatus,  the 

1  Jour,  of  Gas  Lighting,  '75,  798  (1900);  80,  1277  (1902), 
*Berichte,27,  1101. 


ILLUMINATING  GAS  AND  NATURAL  GAS  165 

bulbed  tube  is  disconnected  and  washed  into  an  Erlenmeyer  flask 
of  about  150  c.c.  capacity,  the  bulbed  tube  being  rinsed  with 
50  c.c.  of  picric  acid  from  a  pipette.  The  flask  is  then  closed 
with  a  rubber  stopper  carrying  a' glass  tube  through  which  most 
of  the  air  is  sucked  from  the  flask  by  a  filter  pump  in  order  that 
it  may  not  blow  up  when  heated  later.  The  evacuated  flask  is 
then  placed  in  a  water  bath  which  is  maintained  at  the  boiling 
temperature  for  an  hour.  Rutten1  says  that  it  is  sufficient  to 
heat  to  40°  C.  for  half  an  hour.  The  flask  is  then  removed  and 
allowed  to  cool  when  the  naphthalene  picrate  will  have  recrystal- 
lized  as  a  definite  compound  CioH8.  CeH^OHXNC^s-  This  is 
filtered  off  and  an  aliquot  part  of  the  filtrate  is  titrated  with 
alkali.  The  difference  between  the  amount  of  alkali  required 
for  this  titration  and  that  which  would  have  been  required  on  a 
blank  titration  gives,  when  calculated  for  the  whole  volume  of 
picric  acid  present,  the  naphthalene  absorbed.  One  cubic  centi- 
meter of  N/5  Ba(OH)2  is  equivalent  to  0.0256  grm.  naphthalene. 
If  great  accuracy  is  not  required  the  heating  of  the  naphthalene 
picrate  in  its  solution  may  be  dispensed  with. 

When  gas  freed  from  tar  particles  but  otherwise  unpurified 
is  to  be  tested  for  naphthalene,  it  must  be  freed  from  ammonia 
and  hydrogen  sulphide,  which  affect  the  titration.  The  gas 
must  not  be  allowed  to  cool  below  the  temperature  of  the  main 
during  this  purification  process  or  naphthalene  may  deposit. 
The  purifying  train  may  be  placed  in  an  oven  such  as  that  shown 
in  Fig.  38,  placed  so  that  it  is  in  close  proximity  to  the  main 
and  heated  to  the  desired  temperature.  The  first  washer 
may  contain  lead  acetate,  the  second  a  dilute  acid  and  the  third 
water.  The  tube  with  picric  acid  must  not  be  placed  in  the 
oven  since  naphthalene  will  not  be  absorbed  by  a  warm  solution, 
but  must  be  immediately  outside.  If  naphthalene  is  deposited 
in  the  glass  connecting  tube  it  may  be  vaporized  and  driven 
forward  by  heat.  Where  much  naphthalene  is  present  two 
bulbed  tubes  should  be  used  in  series  and  if  much  precipitate 
appears  in  the  second  tube  the  liquid  in  the  first  tube  should 
be  renewed  since  a  dilute  solution  of  picric  acid  does  not  remove 
naphthalene  completely.  The  precipitated  naphthalene  is  es- 
timated in  the  same  manner  as  in  the  case  of  purified  gas. 

1  Jour,  fiir  Gasbel,  52,  694  (1909). 


166  GAS  AND  FUEL  ANALYSIS 

Where  naphthalene  must  be  estimated  in  crude  gas  still 
containing  suspended  tar  and  it  is  desired  to  separate  the 
naphthalene  present  as  vapor  in  the  gas  from  that  which  is 
carried  in  the  dissolved  tar  particles,  the  method  becomes 
still  more  complicated.  The  method  devised  by  the  author1 
to  separately  determine  the  naphthalene  present  as  vapor  in 
the  gas  from  that  which  is  carried  in  the  dissolved  tar  particles 
involves  precipitation  of  naphthalene  as  the  picrate  with 
subsequent  recovery  of  the  naphthalene.  Considerable  care 
is  necessary  in  sampling  gases  which  contain  tar,  if  it  is  desired 
to  distinguish  between  the  naphthalene  actually  present  as 
vapor  in  the  gas  and  that  existing  dissolved  in  the  fine,  mist- 
like  particles  of  tar  suspended  in  the  gas  and  which  will  be 
removed  later  by  mechanical  scrubbing.  It  is  out  of  the  question 
to  collect  a  tank  of  gas,  say  from  the  foul  main,  and  transport 
it  to  the  laboratory  for  examination.  The  condensation  and 
separation  of  tarry  products  in  the  gas  holder  would  nullify 
the  value  of  the  figures  obtained.  It  is  necessary  to  separate 
the  suspended  tar  and  remove  the  naphthalene  before  change  of 
temperature  has  had  time  to  alter  the  conditions  prevailing 
at  the  point  of  sampling.  This  requires  that  the  tar  vapors 
shall  be  mechanically  filtered  from  the  gas  without  any  change 
in  temperature.  The  result  is  attained  by  inserting  horizontally 
into  the  main  a  glass  tube  about  1/2  in.  in  diameter  filled  with 
glass  wool  or  asbestos  fiber.  This  tube  should  project  into  the 
main  at  least  6  in.  and  at  as  short  a  distance  outside  the  main 
as  possible  should  connect  with  the  picric  acid  absorbing  train, 
and  then  with  a  gas  holder  of  about  1  cu.  ft.  capacity  and  of 
known  volume  as  shown  in  Fig.  2  of  Chapter  I.  The  strong 
solvent  power  of  tar  for  naphthalene  renders  it  absolutely 
essential  that  the  gas  shall  not  be  scrubbed  by  passing  through 
cold  tar,  as  would  be  the  case  if  the  tube  for  separation  of  the 
tar  were  placed  outside  the  main  and,  for  example,  connected 
to  a  pet  cock.  After  the  sample  has  been  drawn,  the  picric 
acid  contains  the  naphthalene  and  tar  which  were  still  present 
in  the  gas  as  vapor.  The  solution  and  precipitate  is  washed 
into  a  200  c.c.  Erlenmeyer  flask  and  treated  with  alkali  to  neu- 
tralize the  picric  acid.  It  is  our  custom  to  add  here  an  excess 

*Proc.  Mich.  Gas.  Ass.,  1904;  1905,  83. 


ILLUMINATING  GAS  AND  NATURAL  GAS 


167 


of  solid  alkali,  making  an  almost  saturated  solution  when  hot, 
merely  to  prevent  so  much  moisture  being  carried  into  the  dry- 
ing tube.  As  this  addition  of  solid  alkali  makes  the  solution  hot, 
it  should  not  be  added  until  just  before  the  apparatus  is  con- 
nected up  so  as  to  avoid  loss  of  naphthalene.  If  the  glass  con- 
necting tube  contains  naphthalene  deposited  from  the  gas  by 
condensation  the  tube  should  be  broken  into  fragments  and 
dropped  into  the  same  flask. 

The  flask  is  then  corked  with  a  stopper  carrying  two  glass 
tubes,  one  long  enough  to  reach  nearly  to  the  bottom  of  the 
flask  and  the  other  terminating  just  below  the  cork  and  extending 
above  the  cork  to  make  connections  to  the  tube  containing 


Glass  Sleeve*' 
Covered  with 

Rubber 


FIG.  37. — Details  of  naphthalene  train. 

lime  and  phosphorus  pentoxide  as  shown  at  A  of  Fig.  37.  At 
the  other  end  of  the  drying  tube  B  close  connection  is  made  to  a 
small  weighed  U  tube  C  which  can  be  immersed  in  ice  water. 
The  tube  containing  the  asbestos  and  tar  is  connected  directly 
to  a  similar  drying  tube  and  U  tube.  The  arrangement  of  the 
train  is  shown  in  Fig.  37  and  the  whole  set  in  the  oven  is 
shown  in  Fig.  38.  The  oven  is  heated  to  70°-80°  C.  and  air 
slowly  drawn  through  the  system,  volatilizing  the  naphthalene 
and  moisture  in  the  tar.  The  moisture  is  taken  up  by  the 
dryer — lime  and  phosphorus  pentoxide — while  the  naphthalene 
passes  on  to  be  frozen  out  in  the  U  tube  placed  directly  out- 
side of  the  oven  in  a  trough  filled  full  of  cracked  ice.  The  analysis 


168 


GAS  AND  FUEL  ANALYSIS 


is  complete  when  the  weight  of  the  naphthalene  U  tube  becomes 
constant  or  very  nearly  so  at  consecutive  weighings  after  a 
two-  or  three-hour  interval.  The  volatilization  of  the  naphthalene 
from  the  gas  is  usually  complete  in  six  hours.  The  time  required 
for  an  analysis  of  tar  varies  with  the  amount  of  tar  in  the  sample 
and  usually  takes  thirty  or  forty  hours  for  standpipe  samples 
when  the  weight  of  tar  amounts  to  8  or  10  grm.  When  the 
analysis  is  complete,  the  tar  volatilizing  tube  is  again  weighed, 
the  loss  giving  the  weight  of  moisture  and  naphthalene  given 
off.  Having  the  weight  of  naphthalene  in  the  U  tube,  we  have 
the  weight  of  moisture  also,  which,  however,  is  at  best  only 


Gh 


Thermometer 
Front 


Removable 
Side 


1 1  FIG.  38. — Oven  for  naphthalene  determinations. 

approximate,  because  there  is  always  more  or  less  light  oil,  such 
as  benzene,  given  off  from  the  tar  with  the  moisture  and  naphtha- 
lene, which  cannot  easily  be  estimated.  Finally  the  volatilizing 
tube  is  set  in  a  Soxhlet  extractor  and  the  remaining  contents 
extracted  with  chloroform  until  free  of  all  soluble  material. 
After  drying,  the  tube  is  weighed,  this  giving  the  weight  of  free 
carbon  in  the  tar.  . 

The  oven  used  is  of  galvanized  iron  and  is  20  in.  high  by  16  in. 
wide  by  14  in.  deep.  It  is  shown  in  Fig.  38  and  is  arranged  so 
that  eight  samples  may  be  worked  at  a  time.  The  drying  train 
consists  of  a  heavy  glass  tube  about  1/2  in.  internal  diameter 
and  12  in.  long.  It  contains  broken  lime  for  about  two-thirds  of 


ILLUMINATING  GAS  AND  NATURAL  GAS  169 

its  length  and  phosphorus  pentoxide  thoroughly  incorporated  in 
glass  wool  for  the  other  one-third.  This  introduction  of  the  glass 
wool  with  the  phosphorous  pentoxide  prevents  the  gas  from 
forming  channels  in  the  latter  and  thus  aids  in  rendering  the  ex- 
traction of  moisture  complete  before  reaching  the  napthalene 
U  tube.  The  lime  used  must  be  extremely  rapid  in  its  reaction 
with  water  in  order  to  avoid  too  great  expense  for  phosphorus 
pentoxide.  It  may  be  readily  made  by  igniting  crushed  lime- 
stone to  a  dull  red  heat  for  two  hours  in  a  muffle.  If  the  lumps  of 
lime  are  too  small,  the  expansion  attendant  upon  their  slacking 
will  crack  the  tube.  If  the  lumps  are  too  large,  the  gas  will  not  be 
dried  sufficiently.  A  satisfactory  mixture  is  obtained  by  taking 
everything  that  will  pass  a  four-mesh  sieve  and  will  not  pass  a 
twelve-mesh.  Connection  with  the  naphthalene  U  tube  is  made 
as  shown  in  Fig.  37  at  C,  through  a  glass  sleeve  made  air  tight  by  a 
piece  of  rubber  tubing  placed  over  the  whole.  This  prevents 
the  naphthalene  from  coming  in  contact  with  the  rubber.  It  is 
well  known  that  rubber  absorbs  naphthalene.  Nevertheless, 
it  has  been  found  safe  to  use  rubber  stoppers  in  the  volatilizing 
oven.  Rubber  stoppers  in  frequent  use  absorb  all  they  can 
take  up  and  after  a  few  runs  cause  no  further  trouble. 

This  method  allows  the  estimation  of  napthalene  as  vapor  in 
the  gas,  and  of  water,  non-volatile  tar,  free  carbon  and  naptha- 
lene in  the  suspended  tar.  The  separation  of  the  water  and  non- 
volatile tar  is  not  very  accurate,  the  light  oils  which  are  vaporized 
by  the  air  drawn  through  being  reported  as  water.  The  estima- 
tion of  naphthalene  is,  however,  quite  accurate.  The  air  passing 
through  will  leave  the  system  saturated  with  naphthalene  at  the 
temperature  of  ice  water,  but  this  loss  need  not  amount  to  over  a 
milligram  for  each  ten  hours'  run.  It  is  possible  that  the  naptha- 
lene may  be  contaminated  by  other  hydrocarbons  and  the  naptha- 
lene deposit  is  sometimes  slightly  oily  and  has  a  low  melting 
point. 

9.  Ammonia. — Crude  coal  gas  before  scrubbing  may  contain  as 
much  as  three-quarters  of  a  per  cent,  of  NH3  by  volume.  After 
the  gas  has  traversed  the  scrubbers  the  amount  of  ammonia 
should  be  reduced  to  a  trace.  The  amount  of  NH3  permissible 
in  purified  gas  in  Massachusetts  and  New  York  is  10  grains  per 
100  cu.  ft.  It  is  not  difficult  to  conform  to  this  requirement. 


170  GAS  AND  FUEL  ANALYSIS 

The  gas  to  be  tested  is  bubbled  through  standard  acid,  suc- 
tion being  produced  by  an  aspirator  holding  a  cubic  foot,  which 
also  acts  as  a  measuring  device.  The  excess  of  acid  is  then 
titrated  back  with  standard  alkali,  cochineal  being  used  as  an 
indicator.  If  the  gas  contains  much  suspended  tar  the  end  of 
the  titration  cannot  be  observed  sharply  and  it  is  necessary  to 
make  the  solution  alkaline  and  redistill  the  ammonia  into  standard 
acid  before  titrating.  One  cubic  centimettter  of  N/io  acid  equals 
0.017  grm.  NH3. 

10.  Cyanogen. — Cyanogen  compounds  exist  in  small  amounts 
in  unpurified  gas.  In  the  purification  process  they  are  partly 
removed  in  the  ammonia  scrubbers  and  largely  in  the  iron-oxide 
purifiers  or  in  special  scrubbers  containing  compounds  of  iron. 
The  gas  is  estimated  by  bringing  it  into  contact  with  an  alkaline 
solution  carrying  suspended  ferrous  hydroxide  and  titrating  the 
resultant  ferrocyanide.  The  method  according  to  Mueller1  is  as 
follows : 

"To  determine  the  amount  of  cyanogen  in  gas,  the  cyanogen  is 
converted  into  potassium  ferrocyanide  by  passing  the  gas  through  a 
caustic  potash  solution  containing  freshly  precipitated  ferrous  hydrate 
in  suspension.  After  filtering,  the  potassium  ferrocyanide  is  determined 
in  the  clear  solution  by  acidifying  and  titrating  with  a  standard  solution 
of  zinc  sulphate  until  all  ferrocyanide  has  been  ^  precipitated  as  zinc 
ferrocyanide.  The  end  reaction  is  determined  as  follows:  A  drop  of 
a  1  per  cent,  solution  of  ferric  chloride  is  put  on  a  piece  of  white  filter- 
paper  absolutely  free  from  iron.  A  drop  of  the  liquid  being  tested  is 
then  put  on  the  paper  near  the  drop  of  ferric  chloride  so  that  the  liquor 
as  it  spreads  out  on  the  paper  will  come  in  contact  with  the  ferric 
chloride.  Care  must  be  taken  that  the  precipitate  of  zinc  ferrocyanide 
does  not  come  in  contact  with  the  iron  solution.  As  long  as  there  is 
any  ferrocyanide  left  in  solution,  a  blue  color  will  appear  where  the 
two  drops  come  in  contact  due  to  the  formation  of  prussian  blue. 
When  all  ferrocyanide  has  been  precipitated  this  color  will  no  longer 
appear,  which  indicates  the  end  point  of  the  titration.  The  zinc  sul- 
phate solution  is  made  by  dissolving  approximately  5  grm.  of  pure  zinc 
sulphate  in  1  liter  of  water  with  the  addition  of  10  c.c.  of  sulphuric 
acid.  This  solution  is  standardized  with  a  solution  of  10  grm.  of  potas- 
sium ferrocyanide  (K4Fe(CN)6.  3H20)  dissolved  in  water  and  diluted 
to  1  liter.  Twenty-five  cubic  centimeters  of  the  potassium  ferrocyanide 

1  Proc.  Am.  Gas  InsL,  5,  249  (1910). 


ILLUMINATING  GAS  AND  NATURAL  GAS 


171 


Jit 


solution  are  put  into  a  beaker  and  titrated  with  the  zinc  sulphate 
solution,  the  end  reaction  being  determined  as  above.  One  cubic 
centimeter  of  the  ferrocyanide  solution  is  equivalent  to  0.0570  grains 
of  cyanogen,  from  which  the  value  of  jbhe  zinc  solution  is  calculated. 

"To  test  for  cyanogen  in  gas  put  15  c.c.  of  a  10  per  cent,  ferrous 
sulphate  (FeS04.  7H20)  solution  into  each  of  three  wash-bottles.  Add 
15  c.c.  of  20  per  cent,  caustic  potash  solution  to  each  bottle  and  pass 
about  3  cu.  ft.  of  gas  through  these  bottles  at  the  rate  of  about  1  cu. 
ft.  per  hour.  Rinse  the  contents  of  the  bottles  into  a  beaker,  add  20 
c.c.  more  of  the  caustic  potash  solution  and  heat  to  boiling.  Filter 
and  wash  with  hot  water  until  a  few  drops  of  the  nitrate  no  longer 
show  a  blue  color  when  acidified  and  tested  with  a  drop  of  1  per  cent, 
ferric  chloride  solution.  Transfer  the  filtrate  to  a  500  c.c.  graduated 
flask,  dilute  to  the  mark  and  shake  well.  Take 
100  c.c.  of  this  solution  and  transfer  to  a  beaker  c 

by  means  of  a  pipette.  Slowly  add  dilute  sul- 
phuric  acid  (sp.  gr.  about  1.5)  stirring  constantly 
until  the  solution  becomes  slightly  acid  toward 
litmus.  Then  run  in  the  zinc  sulphate  solution 
a  few  drops  at  a  time  until  the  drop  test  as  ex- 
plained above  shows  that  the  ferrocyanide  has 
all  been  precipitated.  From  the  amount  of  zinc 
sulphate  solution  used  the  amount  of  cyanogen 
in  the  gas  is  calculated." 

11.  Specific  Gravity.  —  The  simplest 
method  of  determining  the  specific  gravity 
of  gases  makes  use  of  the  law  that  different 
gases  streaming  through  a  given  orifice  at 
the  same  temperature  and  pressure  flow 
through  the  orifice  at  a  rate  inversely  pro- 
portional to  the  square  root  of  their  specific 
gravity.  Since  the  time  of  flow  is  inversely 
proportional  to  the  rate,  the  specific  gravity 
becomes  proportional  to  the  square  of  the 
time  of  flow.  Bunsen  devised  an  inge- 
nious instrument  to  measure  specific  grav- 
ities in  this  way  and  Schilling  later  gave  it  the  form  which  is 
shown  in  Fig.  39.  It  consists  of  a  glass  cylinder  open  at  the  bottom 
and  fastened  to  a  metal  base  which  keeps  it  vertical  within  the 
larger  cylinder  of  water.  It  is  closed  at  the -top  by  a  metal  cap 
carrying  two  cocks.  A  is  for  the  introduction  of  the  gas  to  be 


r 


FIG.  39.— Schilling's 
specific  gravity  appa- 
ratus. 


-  172  GAS  AND  FUEL  ANALYSIS 

tested.  B  is  a  three-way  cock  which  in  one  position  discharges 
the  gas  through  a  side  arm  to  flush  the  apparatus.  When  this 
cock  is  in  the  vertical  position  the  gas  passes  through  a  small 
opening  in  a  platinum  plate  at  C.  The  apparatus  should  be 
standardized  against  air  each  time  it  is  used.  The  calibration 
is  made  by  opening  the  air  cock  and  raising  the  inner  cylinder 
until  it  is  nearly  out  of  water.  It  will  then  be  filled  with  air. 
After  closing  both  cocks  it  is  to  be  again  lowered  into  the  cylinder 
of  water.  The  observer  opens  the  cock  B  so  that  the  air  streams 
out  through  the  capillary  platinum  opening,  starts  a  stop  watch 
as  the  meniscus  passes  the  lower  mark  on  the  gas  tube  and  stops 
the  watch  as  it  passes  the  upper  mark.  The  instrument  is  now 
thoroughly  flushed  with  gas  and  the  time  required  for  the  volume 
of  gas  between  the  two  calibration  marks  to  stream  out  of  the 
opening  is  determined  in  the  same  way.  The  calculation  then 
follows  from  the  formula 

sp.  gr.  gas    t2  gas 
sp.  gr.  air  ~~  t2  air 

12.  Natural  Gas. — Natural  gas  is  ordinarily  distributed  and 
used  without  any  attempt  at  purification.  There  is,  therefore, 
much  less  call  for  analysis  of  this  product.  The  most  important 
determination  is  that  of  heating  value,  which  is  carried  out  in  a 
gas  calorimeter  asttjescribed  for  illuminating  gas  in  Chapter  VII. 
If  the  burner  of  tne  calorimeter  is  adjusted  for  coal  gas  it  will 
have  to  be  readjusted  for  the  natural  gas  and  a  different  tip  may 
have  to  be  inserted.  The  volume  of  the  natural  gas  should  be 
controlled  to  give  about  the  same  rise  in  temperature  in  the  calor- 
imeter as  is  desirable  for  coal  gas.  When  a  knowledge  of  the 
total  sulphur  is  desired  it  is  estimated  by  the  method  of  §  7  of 
this  chapter.  The  chemical  composition  of  the  gas  is  character- 
ized by  very  small  amounts  of  CO 2,  02  and  unsaturated  hydro- 
carbons. The  chief  constituent  is  usually  methane  with  variable 
amounts  of  ethane  and  higher  homologues.  Some  gases  contain 
enough  gasoline  vapors  to  make  it  pay  to  condense  them  by  com- 
pression and  refrigeration.  Burrell1  reports  that  the  specific  grav- 
ity of  the  gas  gives  good  indication  of  its  value  for  this  purpose. 
Pittsburgh  natural  gas  with  a  specific  gravity  of  0.64  when  com- 

1  Bull.  U.  S.  Bureau  of  Mines. 


ILLUMINATING  GAS  AND  NATURAL  GAS 


173 


pared  with  air,  does  not  yield  commercial  quantities  of  gasoline 
Gases  with  specific  gravity  of  0.95  to  1.60  yield  commercially 
from  one  to  five  gallons  of  75  to  98°  Be*  gasoline  per  thousand 
cubic  feet  of  gas.  Heavy  oils  of  various  sorts  may  also  be  used 
as  absorbents  for  gasoline  vapors.  Since,  however,  methane  is 
also  decidedly  soluble  in  oils  the  absorptive  value  of  the  oil  for 
methane  must  be  previously  determined.  The  United  States 
Geological  Survey1  gives  the  following  as  the  average  composi- 
tion of  natural  gas  from  the  three  large  fields  of  the  United  States. 


Average, 
Pa.  and  W.  Va. 

Average, 
Ohio  and  Ind. 

Average, 
Kas. 

CO2                                   

0  05 

0  20 

0  30 

H2S 

0  00 

0  15 

0  00 

O2          

trace 

0.15 

0  00 

CO                                      

0  40 

0  50 

1  00 

H2 

0  10 

1  50 

0  00 

CH4        

80.85 

93.60 

93  65 

Other  hydrocarbons  .  . 
N2  

14.00 
4.60 

0.30 
3.60 

0.25 
4.80 

Mineral  Resources  of  U.  S.,  1909,  2,  297. 


CHAPTER  XIII 
LIQUID  FUELS 

1.  Introduction. — The  liquid  fuel  most  frequently  used  is 
petroleum  in  either  a  crude  or  semi-refined  form.  Coal  tar  and 
tar  products  rank  next  in  importance.  Alcohol  may  become 
important  in  the  future.  These  fuels,  which  are  to  be  burned 
directly,  are  usually  blown  into  the  furnace  in  a  fine  spray  by 
means  of  steam  or  compressed  air.  The  main  points  to  be  deter- 
mined are  their  heating  value,  their  behavior  in  the  burner  and 
the  relative  danger  which  attends  their  storage.  Fuels  which 
are  to  be  vaporized  before  combustion,  as  is  the  case  hi  internal 
combustion  engines,  kerosene  lamps,  etc.,  require  more  elaborate 
testfs  which  do  not  come  within  the'scope  of  this  book. 
t/2.  Sampling. — The  main  difficulty  in  getting  a  representa- 
tive sample  of  liquid  fuel  is  caused  by  the  layer  of  water  and  sedi- 
ment which  frequently  accumulates  on  the  bottom  of  a  tank  of 
oil  or  on  the  surface  of  one  of  tar.  The  main  portion  of  the  liquid 
may  also  be  stratified  if  various  grades  have  been  mixed.  The 
U.  S.  Bureau  of  Mines1  recommends  that  the  oil  be  sampled  as 
delivered  and  that  either  a  small  stream  be  run  off  continuously 
to  a  drum  from  which,  after  mixing,  a  smaller  sample  shall  be 
taken,  or  that  at  regular  intervals  a  small  dipperful  shall  be  taken 
from  the  main  stream  and  placed  in  a  mixing  drum.  Where  it  is 
necessary  to  sample  from  a  small  tank,  a  proportional  sample  may 
be  obtained  by  slowly  lowering  a  glass  tube  vertically  through  the 
oil  till  the  lower  end  rests  on  the  bottom.  If  now  the  upper 
end  be  closed  by  the  thumb  a  column  of  liquid  may  be  drawn 
out  which  represents  the  composition  of  the  vertical  section  at 
the  point  of  sampling.  /  For  large  tanks  the  glass  tube  is  replaced 
by  one  of  tin  carrying  throughout  its  length  a  stiff  wire  on  whose 
jower  end  is  a  tapering  cork.  When  the  cork  hits  the  bottom 

1  Technical  Paper  3,  Bureau  of  Mines.  Specifications  for  the  Purchase  of 
Fuel  Oil  for  the  Government  twin  Directions  for  Sampling  Oil  and  Natural 
Gas. 

174 


LIQUID  FUELS  175 

of  the  tank  as  the  tube  is  lowered,  it  is  forced  up  into  the  tube, 
sealing  the  latter  so  that  the  sample  may  be  drawn  to  the  surface 
without  leakage.  In  default  of  a  sampling  tube  a  corked  empty 
bottle  with  a  string  tied  to  the  cork  may  be  lashed  to  a  stick 
and  be  used.  When  the  bottle  Kas  been  lowered  to  the  desired 
depth  a  pull  on  the  string  removes  the  cork  and  allows  the  bottle 
to  fill  with  oil  which  can  be  withdrawn  and  form  part  of  a  com- 
posite sample. 

3.  Heating  Value. — The  heating  value  of  liquid  fuels  may  be 
determined  in  either  the  bomb  or  Parr  calorimeter  in  accordance 
with  the  general  directions  in  Chapters  XVI  and  XVII.  Some 
difficulty  in  combustion  will  be  experienced  since  all  the  com- 
pounds volatilize  very  rapidly  during  combustion  and  there  is 
danger  that  some  of  the  vapors  may  break  through  the  flame 
zone  without  being  completely  burned.  Incomplete  combustion 
may  usually  be  detected  on  opening  the  calorimeter  by  the  odor, 
and  the  presence  of  soot  on  the  inside  of  the  cover.  The  difficulty 
becomes  greater  with  volatile  liquids  like  gasoline  or  alcohol,  both 
because  of  their  greater  volatility  in  the  calorimeter  and  because 
of  the  difficulty  of  weighing  the  sample  accurately. 

Slightly  volatile  liquids  such  as  tar  and  heavy  petroleum  oils 
may  be  weighed  directly  into  the  capsule  of  the  bomb  calorimeter 
and  burned  completely,  if  oxygen  under  25  atmospheres  pressure 
is  used.  It  is  advisable  to  place  on  the  oil  a  small  weighed  pellet 
of  sugar  or  benzoic  acid  to  start  combustion.  More  volatile 
liquids  must  be  weighed  in  thin-walled  bulbs  of  about  0.5  c.c. 
capacity  with  capillary  necks  which  the  analyst  may  blow  for 
himself  out  of  fine  glass  tubing.  These  are  filled  by  warming 
the  weighed  bulb  and  immersing  the  open  neck  in  the  liquid. 
Contraction  of  the  air  in  the  bulb  draws  up  a  little  of  the  liquid 
and  by  repetition  of  the  process  the  bulb  may  be  filled.  The  capil- 
lary neck  may  then  be  sealed  close  to  the  bulb  with  a  small  blow- 
pipe flame.  The  increase  in  weight  of  the  bulb  plus  the  portion 
of  the  neck  fused  off  gives  the  weight  of  oil  in  the  sample.  The 
sealed  bulb  is  placed  on  the  capsule  of  the  calorimeter  and  around 
it  is  piled  about  0.25  grm.  of  sugar  or  benzoic  acid  in  contact  with 
the  fuse  wire.  The  combustion  of  this  material  breaks  the  bulb 
and  ignites  the  contents.  Richards  and  Jesse1  have  shown  that 

1  Jour.  Am.  Chem.  Soc.,  32,  268  (1910). 


176  GAS  AND  FUEL  ANALYSIS 

even  this  method  fails  to  give  complete  combustion  with  volatile 
liquids  like  benzene.  They  recommend  the  following  procedure 
as  successful. 

"The  benzene  in  a  very  thin  glass  bulb  was  placed  in  the  bottom  of 
a  narrow  platinum  crucible,  2  cm.  in  diameter  and  2.5  cm.  high.  A  few 
millimeters  above  the  bulb  was  fixed  a  small  platform  of  thin  glass 
bearing  a  weighed  quantity  of  powdered  sugar.  The  passage  of  a  cur- 
rent through  the  coil  of  iron  wire  ignited  the  sugar,  which  in  its  turn 
burst  the  bulb  and  ignited  the  benzene  at  a  moment  when  the  whole 
top  of  the  narrow  crucible  was  filled  with  flame  from  the  burning  sugar. 
Thus  none  of  the  benzene  vapor  could  escape  ignition.  The  trouble 
with  the  old  method  had  been  that  the  larger  crucible  was  too  wide. 
Moreover,  the  sugar  had  been  beneath  the  benzene  instead  of  above 
it,  so  that  some  of  the  benzene  escaped  unconsumed.  The  amount 
which  thus  escaped  was  greater  when  there  was  more  nitrogen  present 
than  when  there  was  less.  Obviously,  with  non-volatile  compounds 
like  sugar  the  width  of  the  crucible  would  make  no  difference." 

Gelatine  capsules  such  as  used  by  pharmacists  have  also  been 
recommended  as  containers  for  volatile  oils,  but  their  moisture 
content  changes  so  rapidly  in  the  air  that  it  is  difficult  to  keep 
constant  the  necessary  correction  factor  for  the  gelatine. 

The  heating  value  of  oils  may  also  be  determined  in  the  Parr 
calorimeter,  which  is  described  in  Chapter  XVII.  Non-volatile 
oils  may  be  weighed  directly  into  the  calorimeter  which  already 
contains  the  peroxide  mixture,  and  mixed  thoroughly  with  the 
charge  by  means  of  a  stiff  wire.  Volatile  liquids  may  be  placed  in 
the  calorimeter  in  a  thin-walled  glass  bulb  as  directed  for  the 
bomb  calorimeter,  and  the  charge  of  chemicals  placed  upon  it. 
The  calorimeter  is  then  closed  with  the  cap  provided  and  shaken 
violently  until  the  bulb  is  broken  and  the  oil  is  mixed  with  the 
peroxide.  A  correction  in  addition  to  those  specified  in  Chapter 
XVII  must  be  deducted  for  the  heat  liberated  by  reaction  between 
the  peroxide  and  the  glass  of  the  bulb.  Professor  Parr  gives 
this  correction  as  0.017°  C.  per  0.1  grm.  glass. 

The  weight  of  oil  taken  should  be  about  0.3  grm.  and  the  charge 
10  grm.  of  Na202  and  1  grm.  of  KC103.  The  use  of  0.2  grm. 
benzoic  acid  is  also  advantageous.  Care  must  be  taken  that  crude 
petroleum  and  tars  do  not  carry  much  emulsified  water,  for  the 
water  reacts  with  the  peroxide  with  evolution  of  heat.  In  ex- 


LIQUID  FUELS 


111 


treme  cases  a  violent  explosion  may  take  place,  wrecking  the 
calorimeter. 

If  the  oil  is  of  such  a  type  that  it  may  be  burned  without  smoke 
in  a  burner  without  a  wick  and  there  is  at  least  a  pint  of  the  oil 
available,  the  most  convenient  method  of  determining  heat 
value  is  in  a  calorimeter  of  the  Junkers  type  whose  use  for  deter- 
mining the  heating  value  of  gases  is  described  in  Chapter  VII. 
The  apparatus  as  modified  for  liquids  requires  a  suitable  burner 
for  the  oil  which  hangs  upon  a  balance  during  the  determination 


FIG.  40. — Junkers'  calorimeter  for  heating  value  of  oils. 

as  shown  in  Fig.  40.  The  lamp  as  shown  in  the  illustration  requires 
150-200  c.c.  of  oil.  To  start  the  lamp  the  cup  L  is  filled  with 
alcohol  which  is  lighted  to  preheat  the  burner  head,  n.  When  the 
alcohol  is  nearly  burned  away,  air-pressure  is  placed  upon  the 
liquid  by  a  hand  pump  connected  to  m.  The  oil  rises  in  the  bur- 
ner, vaporizes  and  ignites  in  the  alcohol  flame.  The  pumping  is 
continued  until  a  freely-burning  blue  flame  results  when  the  pump 
is  disconnected.  After  the  water  is  flowing  normally  through  the 
calorimeter,  the  lighted  lamp  is  inserted  and  centered  in  the  com- 
bustion space.  When  equilibrium  has  been  reached,  the  balance 

12 


178  GAS  AND  FUEL  ANALYSIS 

is  brought  to  zero  by  proper  adjustment  of  weights  in  the  pan 
and  the  experiment  started.  After  a  definite  weight  of  oil, 
usually  5  or  10  grm.,  has  been  burned,  the  experiment  is  inter- 
rupted and  from  the  rise  in  temperature  and  the  weight  of 
water  heated  the  heating  value  of  the  fuel  may  be  calculated. 
The  details  and  precautions  are  in  general  the  same  as  given  for 
the  gas  in  Chapter  VII. 

4.  Specific  Gravity. — The  specific  gravity  of  petroleum  products 
is   less  than  1  and   is   usually   reported  on  the   Baume   scale 
for  liquids  lighter   than  water.     Tar   is  usually  heavier  than 
water  and  its  specific  gravity  is  reported  directly.     If  a  sufficient 
quantity  of  material  is  available  and  it  is  not  too  viscous,  the 
specific  gravity  may  be  determined  with  approximate  accuracy 
by  a  hydrometer  spindle.     If  greater  accuracy  is  required  or 
if  only  a  small  sample  is  available  a  pycnometer  or  Westphal 
balance  must  be  used.     If  a  specific  gravity  on  water-free  material 
is  demanded,  the  oil  must  be  put  into  a  flask  without  the  addition 
of  any  diluent  and  distilled  slowly  till  the  water  is  off.     The 
oil  distilled  is  then  separated  from  the  water  and  returned  to 
the  residue  in  the  still  after  it  has  cooled.     A  comparison  of  the 
Baume*  scale  for  liquids  lighter  than  water  and  the  corresponding 
specific  gravities  is  given  in  Table  VIII  of  the  Appendix. 

5.  Moisture. — The   various   methods   for  the   determination 
of  water  in  petroleum  have  been  carefully  examined  by  Allen 
and  Jacobs.1     They  recommend  a  method  which  involves  the 
measurement  of  the  hydrogen  evolved   by  the   action  of  the 
water  on  metallic  sodium  and  also  the  method-  of  distillation, 
either  with  or  without  the  addition  of  water-saturated  toluene 
or  xylene.     The  latter  method   will   probably  give  the   better 
results  in  inexperienced  hands.     It  may  be   used  for  tar  as 
well  as  petroleum  products.     The  toluene  is  added  to  diminish 
the  viscosity  of  the  mass  and  lessen  the  danger  of  foaming 
and  bumping.     Instead  of  toluene,  xylene  or  petroleum  benzine 
with  a  boiling-point  of  110  to  150°  C.  may  be  used.     The  diluent 
must,  however,  be  first  shaken  with  water  and  then  allowed 
to  stand  until  perfectly  clear  in  order  that  it  may  not  dissolve 
any  of  the  water  of  the  sample.     The  sample  of  about   100 
grm.  is  weighed  into  a  distilling  flask  holding  at  least  500  c.c. 

1  Technical  Paper  25,  U.  S.  Bureau  of  Mines,  1912. 


LIQUID  FUELS  179 

and  to  it  is  added  a  roughly  measured  volume  of  100  c.c.  of 
the  diluent  or  200  c.c.  if  the  sample  is  very  viscous.  The 
distillation  is  started  slowly  and  continued  until  the  distillate 
no  longer  comes  over  turbid  and  approximately  as  much  oil 
has  distilled  as  was  added  as  a  diluent.  The  distillate  is  caught 
in  a  graduated  cylinder  and  the  volume  of  water  read  directly 
after  sufficient  time  has  been  given  for  it  to  settle  by  gravity. 
Allen  and  Jacobs  state  that  the  method  may  be  made  accurate  to 
approximately  0.033  grm.  water  for  each  100  c.c.  of  benzene  and 
oil  in  the  distillate. 

The  details  of  a  similar  method  for  the  determination  of 
water  in  tar  as  used  in  the  laboratories  of  the  Barret  Manufac- 
turing Company  have  been  published  by  S.  R.  Church.1  He 
specifies  exactly  the  dimensions  of  the  still,  the  manner  of 
placing  the  theimometer  and  other  details.  The  distillation 
is  to  be  continued  until  the  thermometer  in  the  vapor  has 
reached  205°  C.  He  recommends  a  convenient  form  of  graduated 
separatory  funnel  for  the  distillate  and  states  that  a  clean 
separation  of  the  oil  and  water  can  be  obtained  if  25  c.c.  of 
benzene  is  introduced  into  the  separatory  funnel  before  the 
distillation  is  started. 

6.  Proximate  Analysis. — A  proximate  analysis  in  the  sense 
in  which  it  is  used  in  coal  analysis  is  not  often  made  on  liquid 
fuels  because  they  are  so  largely  volatile  that   the    test  has 
little   meaning.     The   ash   gives   some   measure   of   suspended 
earthy  solids  and  in  the  case  of  tar,  the  fixed  carbon  gives  an 
indication  of  the  amount  of   "free  carbon"   in  the  tar.     It  is 
necessary  to  modify  the  standard  method  for  volatile  matter 
in  coal  by  heating  the  crucible  gently  until  all  foaming  has 
stopped. 

7.  Suspended  Solids. — Suspended  solids  which  in  the  case 
of   crude   petroleums  usually   are  earthy  matters  and  in  the 
case  of  tars  are  fine  particles  of  coke  forming  the  so-called 
"free  carbon"  are  separated  by  filtration  and  washing.     The 
oil  or  tar  is  first  filtered  through  a  30-  or  40-mesh  sieve  to  remove 
coarse  foreign  bodies  accidentally  included.     A  weighed  sample 
of  5  or  10  grm.  is  then  diluted  with  pure  benzene  or  toluene 
until  it  will  filter  readily.     The  solution  is  filtered  through  a 

1  Jour.  Ind.  and  Eng.  Chem.,  3,  228  (1911). 


180  GAS  AND  FUEL  ANALYSIS 

pair  of  weighed  heavy  filter  papers  or  through  a  Gooch  funnel 
and  the  filter  washed  with  more  of  the  warm  solvent  until  the 
extraction  is  complete.  The  filter  is  then  dried  at  105°  C. 
The  increase  in  weight  gives  suspended  solids.  If  there  is 
much  water  in  the  liquid  being  examined  it  may  be  retained 
on  the  filter  in  the  form  of  drops  during  the  first  filtration. 
This  water  may  be  driven  off  by  gentle  heating  and  the  extrac- 
tion of  soluble  material  then  continued. 

8.  Flash  Point. — The  flash  point  of  an  oil  indicates  the  tem- 
perature at  which  the  oil  gives  off  combustible  vapors  with 
sufficient  rapidity  to  form  an  explosive  mixture  with  the  air 
above  it.  The  flash  point  will  depend  upon  the  rate  of  heating 
the  oil,  the  volume  of  air  above  it,  the  rapidity  with  which  the 
air  is  replaced  and  many  other  variables.  It  is  evident  that 
the  conditions  must  be  closely  specified  in  order  that  results 
may  be  of  value.  Unfortunately  there  is  no  standard  method 
as  there  is  for  the  determination  of  volatile  matter  in  coal. 
The  figure  is  of  great  importance  with  kerosene  oil  and  most  of 
the  states  have  definite  and  for  the  most  part  different  regulations 
on  the  subject.  The  older  forms  of  apparatus  were  open  cups. 
The  more  modern  forms  have  closed  cups  and  are  best  exam- 
plified  by  the  Abel  cup  and  its  modifications.  This  consists 
of  a  brass  cup  2  in.  in  diameter  set  in  an  air  bath  which  in  turn 
sits  in  a  relatively  large  water  bath  to  insure  even  heating  of 
the  oil.  The  oil  cup  is  covered  by  a  brass  cover  carrying  a 
thermometer  and  a  sliding  door.  At  a  touch  of  a  spring  the 
door  opens  and  a  small  lamp  carrying  a  minute  flame  is  lowered 
into  the  air  space  above  the  oil.  This  operation  is  repeated 
as  the  temperature  rises  until  a  slight  puff  which  blows  the 
flame  out  indicates  that  there  has  been  an  explosion.  This 
subject  belongs  in  the  domain  of  the  " burning"  oils  rather 
than  the  "fuel"  oils  and  the  reader  is  referred  to  books  on  oil 
analysis  for  details. 


CHAPTER  XIV 
SAMPLING  COAL 

1.  General  Consideration. — However  accurate  an  analysis 
of  coal  may  be,  the  results  are  of  little  value  and  are  often  worse 
than  useless  if  the  sample  submitted  to  the  analyst  is  not  a  repre- 
sentative one.  Elaborate  methods  have  been  worked  out  for 
sampling  gold  and  silver  ores  but  cost  precludes  the  application 
of  anything  but  the  simplest  methods  to  coal.  It  is  manifest 
that  it  is  unwise  to  spend  ten  cents  a  ton  to  determine  whether 
the  price  is  two  cents  a  ton  too  high.  If  we  assume  a  shipment  of 
a  single  car  of  coal  weighing  forty  tons,  which  must  be  sampled 
and  analyzed  by  itself,  it  will  be  seen  that  the  very  moderate 
charge  of  four  dollars  for  this  service  will  add  ten  cents  per  ton 
to  the  price  of  coal.  This  is  probably  10  per  cent,  of  the  cost 
of  the  coal  at  the  mouth  of  the  mine  and  is  an  expense  which  is 
hardly  justifiable. 

However  if  the  test  is  worth  making  at  all  it  must  be  on  a 
sample  which  has  fair  claim  to  representativeness.  The  coal 
sampler  stands  eternally  between  the  devil  of  inadequateness 
and  the  deep  sea  of  excessive  cost.  In  a  few  large  plants  where 
the  coal  is  immediately  crushed  and  removed  to  storage  bins  by 
conveyors  a  representative  sample  may  readily  be  obtained.  In 
most  cases,  however,  the  coal  must  be  sampled  as  it  comes  from 
the  car  and  the  problem  is  more  difficult. 

To  many  people  coal  is  black  and  all  that  is  black  is  coal. 
The  more  careful  observer  may  detect  bits  of  slate,  and  streaks 
or  nodules  of  the  brassy  looking  pyrites.  The  chemist  knows 
that  in  addition  the  fine  particles  which  have  crushed  because  of 
their  greater  friability  differ  in  composition  from  the  lump  coal 
and  are  usually  higher  in  ash,  though  sometimes  the  reverse  is 
the  case,  and  that  coal  is  far  f  rom  being  a  mass  of  uniform 
composition. 

181 


182  GAS  AND  FUEL  ANALYSIS 

DIFFERENCE  IN  COMPOSITION  OF  LUMP  AND  FINE  COAL 

The  following  tests  taken  from  the  author's  record  of  coopera- 
tive tests  undertaken  jointly  by  the  University  of  Michigan  Gas 
Experiment  Station  and  the  United  States  Bureau  of  Mines  to 
determine  the  availability  of  various  coals  for  gas  manufacture 
show  some  interesting  variations.  The  coals  had  mostly  been 
shipped  in  a  small  lots  in  sacks  and  were  therefore  considerably 
crushed  in  transit.  They  were  screened  in  lots  of  about  600  Ib. 
on  a  3/4-in.  bar  screen  preparatory  to  gas  tests  and  the  screenings 
and  lump  coal  separately  sampled. 

The  sampling  of  the  fine  coal  presented  no  difficulty  since  it 
was  already  in  small  lumps  and  could  be  crushed  as  fine  as  de- 
sired. The  lump  coal  could  not  be  finely  crushed  without 
detriment  to  the  gas  tests  and  so  it  was  sampled  by  breaking 
the  large  lumps  and  then  taking  about  two  scoopfuls  which  were 
crushed  and  sampled  as  usual.  Of  the  eleven  coals  tested  in 
this  manner  four,  one  each  from  West  Virginia,  Colorado,  New 
Mexico  and  Wyoming  showed  very  little  difference  between  the 
lumps  and  screenings.  One  coal  showed  decidedly  less  ash  in 
the  screenings  than  in  the  lump  coal.  Six  coals  showed  notice- 
able and  in  some  cases  notable  increases  of  ash  and  sulphur  in 
screenings  with  corresponding  decreases  of  heating  value,  as 
shown  by  the  following  analyses  of  the  coals  calculated  to  a  dry 
basis. 

In  the  coal  from  Hellier,  Kentucky  for  which  there  are  three 
tests,  the  average  heating  value  of  the  screenings  is  1080  B.t.u. 
lower  than  that  of  the  lump.  This  is  entirely  due  to  difference  in 
ash  as  shown  by  the  figures  for  heating  value  figured  to  coal  dry 
and  free  from  ash,  where  the  difference  disappears,  the  average 
heating  value  of  the  screenings  being  only  6  B.t.u.  below  that  of 
the  lump.  The  same  thing  is  true  of  the  other  coals  of  the  list — 
the  variation  in  heating  value  of  lump  and  screenings  disappears  al- 
most completely  when  calculated  to  a  moisture  and  ash-free  basis. 

Sulphur  is  never  lower  in  the  screenings  than  in  the  lump  and 
is  in  some  cases  nearly  twice  as  high. 

The  last  coal  in  the  above  table  differs  from  all  the  others  in 
that  the  screenings  are  much  lower  in  ash  than  the  lump.  It 
might  be  thought  that  the  sample  had  been  labelled  incorrectly 


SAMPLING  COAL 


183 


a  s 


S3 


CO 


i-HOOOOi-Hr-l(MCOl-H 


8»H 
•* 


I>OOOCOCOO>OOI>COO5 
^HCO^COCN  <N<NCO 


COtNCOiOCOCOCO 


CO 
CO 


184  GAS  AND  FUEL  ANALYSIS 

of  it  were  not  for  the  check  afforded  by  analysis  of  the  coke  made 
from  the  lump  coal.  The  coke  contained  25.3  per  cent,  of  ash, 
a  figure  which  agrees  well  with  the  calculated  result  of  24.3  per 
cent.  It  is  evident  that  in  this  coal  the  coal  substance  is  the 
friable  constituent  while  the  ash  forms  a  cementing  material. 
The  heating  value  of  the  dry  screenings  is  1366  B.t.u.  higher 
than  the  lump,  but  when  the  ash  is  eliminated  by  calculation, 
the  difference  drops  to  61  B.t.u. 

These  figures  show  that  the  heating  value  of  lump  coal  may 
vary  as  much  as  2000  B.t.u.  from  that  of  fine  coal  and  that 
usually  the  fine  coal  will  contain  more  ash  and  have  the  lower 
heat  value.  Occasionally  the  reverse  is  the  case.  The  true 
coal  as  reckoned  to  a  moisture  and  ash  free  basis  has  practically 
the  same  heating  value  irrespective  of  its  physical  fineness. 

2.  A  Scoopful  as  a  Sample. — It  is  commonly  held  that  a 
few  scoopfuls  should  be  representative  of  a  carload.  This 
question  was  put  to  a  practical  test  by  Bailey1  who  had  a  lot 
of  3  tons  of  run-of-mine  coal  carted  away  in  wheel  barrows. 
As  each  barrow  was  filled  a  shovelful  of  coal  was  put  into, 
not  one,  but  into  each  of  sixteen  sample  barrels.  After  the 
pile  had  disappeared  there  were  left  the  sixteen  sample  barrels 
each  with  about  125  Ib.  of  coal.  These  samples  were  crushed 
and  sampled  carefully  and  the  ash  in  each  was  determined. 
The  results  were  as  follows: 

Per  cent,  ash 

1 9.68 

2 10.28 

3 13 . 92  Maximum 

4 11.22 

5 10.88 

6 9.80 

7 11.84 

8 10.28 

9 10.10 

10 10.64 

11 10.06 

12 10.72 

13 9 . 46  Minimum 

14 9.66 

15 11.08 

16 11.34 

1  Trans.  Am.  Soc.  Meek.  Eng.,  27,  639  (1906). 


SAMPLING  COAL 


185 


These  samples  which  should  have  given  results  in  close  agree- 
ment show  an  extreme  variation  of  4.46  per  cent,  in  their  ash 
content.  Had  the  heating  values  of  these  samples  been  deter- 
mined they  would  of  course  have  shown  similar  discrepancies. 
If  this  coal  has  been  sold  on  a  premium  and  penalty  basis  and 
the  coal  with  the  average  ash  content  of  10.68  would  have 
been  accepted  without  premium  or  penalty,  the  penalty  on  a 
basis  of  sample  No.  3  might  readily  have  been  six  or  eight 
cents  per  ton.  And  yet  in  this  test  the  sample  consisted  of 
four  or  five  shovelfuls  taken  from  a  lot  as  small  as  3  tons  and 
not  from  a  whole  car  load. 

3.  Influence  of  Lumps  of  Slate. — It  is  manifest  that  if  all 
the  ash  of  coal  were  to  be  concentrated  in  lumps  the  size  of  a 
football,  that  a  single  scoopful  of  coal  would  either  show  no 
ash  or  else  an  exorbitantly  high  amount.  The  error  would 
be  much  less  if  the  ash  were  in  lumps  only  the  size  of  walnuts 
and  still  less  if  it  were  more  finely  divided.  Even  if  the  ash 
were  in  large  pieces  if  a  sufficient  number  of  scoops  should  be 
taken  for  analysis  an  average  of  all  the  figures  would  give  a 
correct  result.  Bailey1  gives  the  following  table  derived  partly 
experimentally  and  partly  mathematically  showing  the  relation 
between  the  size  of  the  largest  piece  of  slate  and  the  weight  of 
the  sample  which  must  be  taken  in  order  that  error  in  sampling 
shall  not  cause  an  error  of  over  1  per  cent,  in  the  ash. 


Size  of  slate, 
inches 

Wt.  largest  piece  of 
slate,  pounds 

Original  sample  should 
weigh,  pounds 

4 
3 
2 

1 

6.7 
2.5 
0.75 
0.12 

39,000 
12,500 
3,800 
600 

0.75 

0.046 

230 

0.50 

0.018 

90 

Since  there  are  very  few  shipments  of  coal  other  than  the 
small  sizes  of  anthracite  which  may  not  contain  pieces  of  slate 
weighing  a  pound  it  is  evident  that  on  this  basis  a  sample  of 
less  than  2  tons  cannot  be  considered  representative.  Any 
smaller  sample  whether  it  be  drawn  from  a  wagon  load  or  a 

1  Jour.  Ind.  and  Eng.  Chem.,  1,  176  (1909). 


186  GAS  AND  FUEL  ANALYSIS 

train  of  cars  cannot  be  considered  as  representative  of  anything 
except  itself. 

4.  Taking  a  Sample. — It  is  fatal  for  a  sampler  to  try  and 
pick  an  average  sample  by  taking  what  seems  to  him  a  fair 
proportion  of  coarse  and  fine,  and  rejecting  material  that  looks 
either  exceptionally  good  or  bad.     The  only  way  is  to  determine 
how  a  most  representative  sample  may  be  secured  in  a  reasonable 
manner  and  then  to  carry  out  the  operation  as  mechanically 
as  possible. 

If  the  sample  is  being  taken  from  a  wagon  the  shovel  should 
be  run  along  the  bottom  of  the  wagon  after  enough  has  been 
unloaded  to  allow  the  coal  to  assume  its  natural  slope.  The 
same  procedure  may  be  followed  when  coal  is  being  shovelled 
from  flat-bottomed  cars.  Where  cars  or  wagons  are  being 
dumped  the  scoop  may  be  held  in  the  stream  of  falling  coal. 
If  cars  are  to  be  sampled  before  unloading,  a  trench,  or  better 
two  trenches,  each  12  in.  deep  should  be  dug  "across  the  car  in 
order  to  remove  excess  of  dust  and  cinder  as  well  as  snow  which 
may  have  collected  in  the  top  layers.  The  sample  is  to  be 
taken  from  the  bottom  of  the  trench.  It  is  evident  that  coal 
sampled  in  this  way  will  contain  too  small  a  proportion  of  fine 
coal,  most  of  which  will  have  sifted  to  the  floor  of  the  car.  It 
is  therefore  preferable  to  sample  during  unloading. 

If  it  is  necessary  to  determine  the  moisture  in  a  car  of  coal 
which  arrives  wet  or  covered  with  ice  the  problem  of  sampling 
becomes  even  more  complex.  Fortunately,  specifications  are 
usually  based  on  dry  or  air-dry  coal  so  that  the  accidental 
moisture  acquired  in  transit  is  not  usually  of  importance. 

5.  Mine  Sampling. — The  methods  of  sampling  coal  in  a  mine 
as  recommended  by  the  U.  S.  Bureau  of  Mines  have  been  fully 
described  by  Holmes.1     He  recommends  that  for  mines  shipping 
200  tons  or  less  daily,  at  least  four  samples  should  be  taken. 
In  general  only  clean,  fresh  coal  should  be  taken  and  weathered 
coal  should  be  avoided.     Before  cutting  a  sample  the  face  of  the 
bed  and  the  roof  is   to  be  cleaned  of  loose  fragments  which 
might  drop  into  the  sample  and  a  band  1  ft.  wide  extending 
from  floor  to  roof  is  to  be  cut  back  at  least  an  inch  to  expose 
fresh  coal.     The  sample  as  cut  from  this  prepared  face  should 

1  Technical  Paper  1,  Bureau  of  Mines,  1911. 


SAMPLING  COAL  187 

include  everything  which  the  miner  includes  in  the  coal  pre- 
pared for  the  market  and  should  exclude  the  thick  partings  and 
large  lenses  of  pyrite  which  are  thrown  out  by  the  miner.  The 
cut  should  be  made  perpendicularly  about  2  in.  deep  and  6  in. 
wide  so  that  there  will  be  about  6  Ib.  of  coal  chips  for  each  foot 
of  thickness  of  the  vein.  These  chips  are  to  be  caught  on 
the  waterproof  sample  blanket  and  crushed  to  pass  a  1/2-in. 
screen.  The  sample  is  then  quartered  down  and  placed  in 
a  tight  sample  can.  All  the  operations  are  to  be  carried 
on  in  the  mine  so  as  not  to  expose  the  coal  to  the  outside 
atmosphere. 

6.  Preparation  of  Sample. — The  initial  sample  must  be  crushed 
and  subdivided  until  it  is  finalty  ready  for  the  chemical  analysis. 
Care  must  be  taken  that  it  does  not  change  during  this  process. 
It  is  almost  impossible  to  prevent  the  moisture  from  changing 
and  where  it  is  necessary  to  deteimine  this,  the  whole  sample 
is  usually  weighed  and  allowed  to  dry  in  a  warm  room  until 
it  has  become  approximately  air-dry,  when  it  is  again  weighed. 
It  is  in  any  case  difficult  to  sample  coal  which  is  very  wet  or 
covered  with  ice  and  a  preliminary  air-drying  is,  where  possible, 
alway  advisable.  The  sample  must  now  be  crushed  and  sub- 
divided. Bailey,  in  the  reference  already  cited,  gives  the 
following  rules  for  subdivision: 

Weight  of  sample  to  be  Should  be  broken 

divided,  pounds  to  inches 

7500 2 

3800 1.5 

1200 1 

460 0.75 

180 0.5 

40 2  mesh 

5 4  mesh 

0.5 8  mesh 

0.25 10  mesh 

Where  a  well-equipped  sampling  laboratory  is  available 
the  crushing  will  of  course  be  easily  accomplished  by  crushers 
and  the  subdivisions  either  made  by  mechanical  samplers 
or  upon  clean  iron  plates.  In  such  cases  there  is  very  little 
liability  to  error  in  this  stage  of  the  process.  In  many  cases, 


188  GAS  AND  FUEL  ANALYSIS 

however,  the  crushing  and  subdivisions  must  be  carried  out 
by  hand,  often  on  the  floor  of  the  boiler  room  and  frequently 
under  even  less  favorable  conditions.  The  first  requisite  is 
cleanliness  of  the  sampling  surface.  It  is  always  preferable  to 
sample  on  a  metal  plate.  A  cement  floor  is  to  be  looked  upon 
with  suspicion  and  not  to  be  used  unless  it  is  hard  and  fails 
to  yield  appreciable  sand  on  vigorous  sweeping.  The  liability 
to  error  is  not  great  while  the  sample  is  large.  When  it  becomes 
pmall  enough  it  should  be  placed  on  oil  cloth  if  a  metal  plate 
is  not  available. 

When  working  with  a  large  sample  the  lumps  may  be  crushed 
by  a  hammer  or  stamp  to  the  size  indicated  and  the  material 
shovelled  up,  one  shovelful  out  of  every  four  going  to  the 
sampling  barrow.  All  the  coal  should  be  shovelled  away  in 
this  manner  and  the  floor  swept  clean.  It  is  not  sufficient  to 
shovel  into  the  sampling  barrow  approximately  one-fourth 
of  the  sample  pile  and  leave  the  other  three-fourths  behind,  for 
this  process  might  include  in  the  sample  all  the  fine  pieces 
resulting  from  one  large  piece  of  slate.  When  the  sample 
has  been  reduced  to  400  or  500  Ib.  it  is  customary  after  crushing 
to  shovel  the  coal  into  a  cone  which  is  shovelled  out  again  into  a 
ring,  care  being  taken  to  distribute  the  coal  on  the  ring  with  a 
circular  motion  in  order  to  distribute  the  fine  pieces  resulting 
from  one  large  piece  of  slate.  This  ring  is  again  to  be  shovelled 
into  a  cone,  the  sampler  going  round  and  round  the  ring  and 
placing  each  shovelful  of  coal  on  the  apex  of  the  coiae  so  that 
it  may  run  down  as  nearly  evenly  as  possible  around  the  cir- 
cumference. The  dust  which  cannot  be  shovelled  up  is  then 
swept  radially  to  the  cone,  the  cone  is  flattened  and  cut  into 
quarters  by  the  shovel.  The  whole  of  one  quarter  including 
the  sweepings  is  then  shovelled  into  a  tight  barrow  or  bucket, 
the  sampling  floor  is  cleared  and  the  process  repeated  until  the 
sample  is  sufficiently  reduced.  The  final  sample  should  weigh 
4  or  5  Ib.  and  be  crushed  to  1/8-in.  size.  It  should  at  once  be 
placed  in  a  tight  bottle  or  can  and  plainly  labelled. 

7.  Preservation  of  Sample. — If  the  percentage  of  moisture 
in  the  coal  is  of  importance  the  sample  should  be  placed  in  an 
air-tight  receptacle  and  kept  in  a  cool  place.  Coal  which  is 
not  finely  powdered  does  not  change  rapidly  but  it  is  advisable 


SAMPLING  COAL 


189 


to  have  the  analysis  made  promptly.  Porter  and  Ovitz1  have 
shown  that  samples  of  coal  evolve  methane  and  carbon 
dioxide  and  absorb  oxygen  for  a  period  of  several  months. 
The  changes  due  to  the  evolution  of  methane  seldom  rise  above 
one-tenth  of  1  per  cent.  The  changes  due  to  addition  of  oxygen 
are  less  certain  but  would  seem  to  be  possibly  as  high  as  1/2  per 
cent.  Parr  has  shown  that  Illinois  coals  may  lose  in  heat  value 
from  1/2  to  1  per  cent,  in  the  first  ten  days  after  mining  and 
during  the  process  of  preparing  the  sample  for  analysis.  The 
rapid  changes  take  place  soon  after  the  coal  is  mined  and  the 
rate  of  change  has  usually  materially  decreased  before  the  coal 
is  sampled  by  the  consumer. 

8.  Usual  Accuracy  of  Sampling. — The  figures  given  by  Bailey 
show  that  an  accuracy  of  1  per  cent,  in  the  ash  is  not  to  be  ex- 
pected by  ordinary  methods.  The  following  tables  give  some 
data  resulting  from  the  sampling  of  two  separate  carloads  of 
coal.  Four  separate  samples  were  taken  from  each  car  after 
loading  at  the  mine  by  an  inspector  of  the  Bureau  of  Mines.  The 
cars  on  arrival  were  sampled  especially  carefully,  one-sixth  of  each 
carload  being  systematically  separated  as  it  was  unloaded  for  the 
initial  sample.  This  initial  sample  was  cut  into  four  separate  ones 
which  were  separately  sampled  and  analyzed.  There  are  eight 
different  samples  from  each  carload  whose  analyses  are  tabulated 
in  the  accompanying  table. 

PITTSBURG  COAL,  A.  A.  15 


Air-dried  coal 

B.t.u.  of  coal 
free  from  mois- 
ture and  ash 

Moisture 

Ash 

S      |  B.t.u. 

Car  at  mine 

No.  1... 

0.95 

6.27 

0.91 

14213 

15319 

No.  2... 

1.00 

5.55 

0.72 

14315 

15318 

No.  3... 

0.98 

6.23 

0.98 

14182 

15284 

No.  4... 

0.96 

6.91 

0.84 

14107 

15295 

Average 

0.97 

6.24 

0.86 

14204 

15304 

Car   as   un- 

No. 1... 

1.11 

5.99 

0.82 

14215 

15301 

loaded 

No.  2... 

0.97 

6.54 

0.93 

14137 

15284 

No.  3... 

1.01 

5.63 

0.80 

14285 

15300 

No.  4... 

1.08 

5.88 

0.81 

14206 

15269 

Average 

1.04 

6.00 

0.84 

14211 

15288 

1  Technical  Paper  2,  Bureau  of  Mines,  1911. 


190 


GAS  AND  FUEL  ANALYSIS 


FAIRMONT  COAL,  A.  A.  16 


1 

Vir-drie 

i  coal 

B.t.u.  of  coal 
free  from  mois- 

Moisture 

Ash 

s 

B.t.u. 

ture  and  ash 

Car  at  mine. 

No.  1... 

1.10 

7.62 

0.67 

13925 

15255 

No.  2... 

1.10 

7.71 

0.64 

13874 

15216 

No.  3... 

.07 

9.23 

0.83 

13678 

15240 

No.  4... 

.17 

6.20 

0.52 

14096 

15217 

Average 

.11 

7.69 

0.66 

13898 

15232 

Car   as   un- 

No. 1... 

.24 

8.87 

0.64 

13671 

15209 

loaded 

No.  2... 

.21 

8.98 

0.69 

13640 

15188 

No.  3... 

.28 

8.89 

0.69 

13638 

15182 

No.  4... 

1.27 

9.06 

0.73 

13604 

15160 

Average 

1.24 

8.95 

0.69 

.13638 

15185 

The  chief  variable  in  these  samples  is  the  ash  which  in  turn 
affects  the  heating  value.  The  accuracy  of  the  analyses  is  at- 
tested by  the  close  agreement  of  the  heating  value  referred  to  coal 
dry  and  free  from  ash.  In  the  Fairmont  coal  the  heating  value 
of  the  coal  taken  at  the  mine  is  noticeably  higher  than  that  sam- 
pled from  the  car,  when  calculated  to  an  ash  and  moisture  free 
basis,  due  possibly  to  escape  of  gas  from  the  freshly  mined  coal. 

The  average  ash  content  of  the  Pittsburgh  coal  is  closely  the 
same  in  the  two  sets  but  in  the  Fairmont  coal  the  average  ash 
as  sampled  from  the  car  at  the  mine  was  1.6  per  cent,  lower  than 
that  obtained  as  the  car  was  unloaded.  As  was  pointed  out 
above,  this  variation  is  a  normal  one  due  to  the  method  of  sam- 
pling. The  variation  in  the  average  heating  value  of  these  two 
series  amounts  to  260  B.t.u.,  a  figure  which  might  easily  cause 
a  difference  in  price  of  five  cents  a  ton. 

Turning  from  averages  to  individual  figures  we  find  a  better 
agreement  with  the  Pittsburgh  than  the  Fairmont  coal,  and  in 
each  series  the  agreement  better  between  the  samples  taken  from 
the  car  as  unloaded,  as  should  have  been  the  case.  The  extremes 
for  the  Fairmont  coal  are  tabulated  as  follows : 


4 

Low  ash 

High  ash 

Difference 

per  cent,  ash 

B.t.u. 

per  cent,  ash 

B.t.u. 

per  cent,  ash 

B.t.u. 

Car  at  mine  
Car  as  unloaded  . 

6.20 
8.87 

14096 
13671 

9.23 
9.06 

13678 
13604 

3.03 
0.19 

418 
69 

The  agreement  between  the   samples   taken   very    carefully 


SAMPLING  COAL  191 

from  the  car  as  unloaded  is  excellent.  The  difference  between 
the  extremes  of  the  samples  taken  from  the  loaded  car  which 
amounts  to  426  B.t.u.  might  readily  cause  a  difference  of  nine 
cents  a  ton  on  the  settlement  price  of  the  coal. 

The  engineers  of  the  U.  S.  Bureau  of  Mines1  have  studied  the 
error  in  sampling  on  ten  different  lots  of  coal.  Each  of  two  in- 
spectors collected  a  sample  of  100  Ib.  from  a  given  lot  of  coal.  In 
lot  a  their  samples  differed  in  heating  value  by  158  B.t.u.  per 
pound  of  dry  coal.  They  then  each  collected  a  second  sample 
of  100  Ib.  and  averaged  the  results  of  this  with  their  first  sample. 
The  difference  between  the  two  collectors  than  dropped  to  132 
B.t.u.  In  the  same  way  they  continued  to  take  successive  samples 
of  100  Ib.  and  average  all  of  their  results  and  after  ten  of  such 
samples  had  been  taken  the  differences  between  the  averages 
for  each  man  was  small.  As  the  result  of  tests  on  ten  different 
lots  of  coal  they  found  that  it  was  necessary  to  collect  and  average 
seven  different  samples  of  100  Ib.  each  in  order  that  the  results 
obtained  by  two  collectors  should  not  differ  by  more  than  50 
B.t.u.  Their  average  results  are  given  in  the  following  table. 

AVERAGE  ERROR  IN  SAMPLING  10  LOTS  OF  COAL  AS  SHOWN 
BY  THE  DISAGREEMENT  IN  HEATING  VALUE  OF  SUC- 
CESSIVE SAMPLES  TAKEN  BY  TWO  COLLECTORS 


Disagreement  between  two 

collectors  in  B.t.u.  per 

pound  dry  coal 


First  sample  of  100  Ib 

Average  of  2  samples  of  100  Ib 

Average  of  3  samples  of  100  Ib 

Average  of  4  samples  of  100  Ib 

Average  of  5  samples  of  100  Ib 

Average  of  6  samples  of  100  Ib 

Average  of  7  samples  of  100  Ib 

Average  of  8  samples  of  100  Ib 

Average  of  9  samples  of  100  Ib 

Average  of  10  samples  of  100  Ib 

Average  of  11  samples  of  100  Ib 

Average  of  12  samples  of  100  Ib 

Average  of  13  samples  of  100  Ib. 


251 

200 

125 

111 

75 

78 

51 

53 

44 

37 

32 

32 

25 


The  Bureau  of  Mines  recommends  that  the  gross  sample  collected 
1  Bui  63,  Bureau  of  Mines. 


192  GAS  AND  FUEL  ANALYSIS 

be  never  less  than  1000  Ib.  In  sampling  cargo  deliveries  of  5000 
and  more  tons  the  recommendation  is  that  the  sample  be  from 
4000  to  5000  Ib.  and  that  the  sample  be  crushed  in  approximately 
500-lb.  lots  from  each  of  which  a  sample  is  sent  to  the  laboratory. 
Four  or  five  analyses  are  usually  made  for  each  cargo  and  the 
results  are  averaged.  Detailed  directions  for  sampling  and  also 
specifications  for  coal  as  used  by  the  Government  are  given  in 
Bulletin  63  of  the  Bureau  of  Mines  entitled  Sampling  Coal  Deliv- 
eries and  Types  of  Government  Specifications  for  the  Purchase  of 
Coal  by  George  S.  Pope.  Copies  may  be  obtained  from  the 
Director  of  the  Bureau  of  Mines  in  Washington. 

9.  Reliability  of  Samples. — It  is  evident  from  the  preceding 
paragraphs  that  it  is  possible  to  sample  crushed  coal  with  fair 
accuracy,  but  that  it  is  not  possible  to  accurately  sample  coal 
containing  large  lumps  without  greater  expense  than  is  usually 
warranted.  The  error  is  largely  an  accidental  one  due  to  the 
inclusion  or  rejection  of  too  many  or  too  few  of  the  larger  pieces 
of  slate  in  the  sample.  There  may  also  be  a  systematic  error  if 
care  has  not  been  taken  to  get  a  proper  proportion  of  coarse  and 
fine  coal.  So  far  as  the  error  is  accidental,  it  will  diminish,  ac- 
cording to  the  law  of  probabilities,  with  increasing  number  of 
samples,  so  that  although  any  one  sample  may  be  in  error  by  3 
per  cent.,  the  average  of  fifty  samples  should  be  quite  accurate. 
Contracts  which  involve  the  delivery  of  coal  throughout  the  year 
may  therefore  be  equitably  settled  on  a  sliding  scale  based  on 
analysis,  for  the  undue  premium  on  one  shipment  will  be  counter- 
balanced by  the  undue  penalty  on  another  and  in  the  course  of 
a  year  a  fair  average  will  have  been  reached.  If  it  is  necessary  to 
determine  accurately  the  value  of  a  single  shipment,  greater  care 
and  expense  is  necessary  than  the  sum  at  issue  will  usually 
warrant. 


CHAPTER  XV 
THE  CHEMICAL  ANALYSIS  OP  COAL 

1.  Introduction. — The  methods  used  in  analysis  of  coal  may 
be  grouped  into  two  main  divisions.     In  ultimate  analysis  the 
aim  is  to  report  as  accurately  as  may  be  the  percentages  of  the 
chemical  elements,  especially  carbon,  hydrogen,  nitrogen,  oxygen 
and  sulphur.     These  elements  are  reported  as  elements  without 
any  attempt  to  indicate  the  manner  in  which  they  are  combined 
in  the  coal.     This  method  of  analysis  is  scientifically  valuable  but 
finds  few  applications  in  technical  work.     In  proximate  analysis, 
on  the  other  hand,  the  attempt  is  made  to  group  the  constituents 
of  the  coal  according  to  certain  physical  properties  which  are 
technically  important  such  as  moisture,  volatile  matter  and  ash. 
This  method  of  analysis  is  of  great  commercial  importance. 
These  two  methods  of  analysis  are  applicable  to  all  forms  of 
solid  and  liquid  fuel — peat,  lignite,  bituminous  coal,  anthracite, 
coke,  petroleum,  tar,  etc. — with  slight  modifications  required  by 
the  physical  properties  of  the  fuel  being  investigated. 

2.  Proximate  Analysis. — The  usual  items  included  in  a  proxi- 
mate analysis  are  moisture,  volatile  matter,  fixed  carbon  and  ash. 
Sulphur  is  frequently  included  in  the  report,  but  is  determined 
separately.     There  is  no  difficulty  in  comprehending  what  is 
meant  by  the  terms  moisture  and  ash.     The  expressions  volatile 
matter  and  fixed  carbon  require  explanation,  for  they  are  merely 
relative  terms  which   can  be  interpreted  only  by  reference  to 
"certain  definite  conditions  of  analysis.     If  coal  be  heated  to  red- 
ness the  heat  will  decompose  a  portion  of  the  coal  substance. 
Part  of  this  decomposed  coal  will  be  evolved  as  a  thick  black 
smoke  which  will  burn  in  the  air  and  part  will  remain  behind 
as  a  solid  coke  or  carbonaceous  reside.     If  tar  or  petroleum 
be    treated    in    this    manner   part   of   the   substance   will   be 
driven  off  in  the  same  form  in  which  it  existed  in  the  oil.     In 
the    case    of    coal   the    material    volatilized    is    formed    only 
through  the  decomposing  action  of  the  heat.     In   proximate 

13  193 


194  GAS  AND  FUEL  ANALYSIS 

analysis  no  attempt  is  made  to  separate  these  two  classes  of 
products.  Everything  which  is  evolved  in  the  process  is  called 
"  volatile."  The  residue  remaining  in  the  crucible  after  this 
process  consists  of  ash  and  a  material  which  is  largely  carbon 
and  which  forms  the  so-called  "  fixed  carbon."  The  percentages 
reported  as  volatile  matter  and  fixed  carbon  will  vary  with 
every  modification  of  the  conditions  of  analysis.  The  mois- 
ture and  ash  are  also  liable  to  vary  with  change  in  detail  of 
method.  It  is  therefore  very  important  that  all  chemists  use 
the  same  method  in  order  that  their  results  may  be  comparable. 
In  18991  a  committee  of  the  American  Chemical  Society  which  had 
made  a  careful  study  of  the  subject  reported  a  scheme  of  analysis 
which  has  been  generally  recognized  as  standard  for  the  United 
States.  In  1910  a  joint  committee  of  the  American  Chemical 
Society  and  the  American  Society  for  Testing  Materials  was 
formed  to  consider  a  revision  of  these  methods,  and  their  sugges- 
tions as  embodied  in  their  preliminary  report2  are  included  in 
this  chapter. 

3.  Preliminary  Examination  of  Sample,. — In  the  preceding 
chapter  on  Sampling  the  precautions  to  be  observed  in  taking 
the  initial  sample  and  in  subdividing  it  were  discussed.  There  is 
no  definite  point  where  the  sampler  is  to  stop  in  his  process  of 
subdivision  and  turn  the  material  over  to  the  chemist,  but  since 
the  sampler  is  in  general  a  field  worker  it  is  customary  to  consider 
his  work  as  ended  when  the  sample  has  been  reduced  in  weight 
sufficiently  to  allow  its  easy  transportation  to  the  laboratory. 
Sometimes  it  is  stated  that  the  sample  sent  to  the  laboratory 
should  weigh  from  3  to  5  Ib. 

The  chemist  receiving  a  sample  should  note  the  nature  of  the 
package  as  well  as  its  marks.  Coal  shipped  in  a  canvas  sack  or  a 
paper  carton  which  is  not  tight  will  almost  certainly  have  changed 
in  moisture  content  and  will  probably  have  lost  some  of  its  finer 
particles.  After  opening  the  package  the  net  weight  of  sample 
and  an  at  least  approximate  estimate  of  its  physical  condition 
should  be  recorded.  Information  as  to  whether  the  sample  as 
received  was  wet  or  dry  and  whether  it  showed  evident  pieces 
of  slate  or  pyrite  is  sometimes  of  importance.  The  size  of  the 

1  Jour.  Am.  Chem.  Soc.,  21,  1116  (1899). 

2  Jour.  Ind.  and  Eng.  Chem.,  5,  517  (1913). 


THE  CHEMICAL  ANALYSIS  OF  COAL  195 

largest  lumps  relative  to  the  size  of  the  sample  shipped  will  give 
some  indication  of  the  care  which  has  been  used  in  the  preparation 
of  the  sample.  The  chemist  should,  for  his  own  protection,  state 
in  his  report  when  the  sample  is  manifestly  a  non-representative 
one,  and  when  insufficient  care  has  been  exercised  in  packing  it 
for  shipment. 

The  1913  report  of  the  Committee  on  Coal  Analysis  recommends 
that  the  size  of  sample  to  be  transmitted  to  the  laboratory  vary 
with  the  size  of  the  coal  as  follows : 


Size  of 

largest  impurities 

Minimum  weight  of  sample 

1/2  in 

75  Ib. 

3/8  in 

30  Ib. 

1/4  in 

91b. 

3/16  to  1/5  ii 

i=4  mesh 

51b. 

1/8  in 

3  to  5  Ib. 

4.  Air-drying. — It  is  inconvenient  to  handle  samples  of  coal 
which  are  wet,  since  they  clog  the  mills  and  cannot  be  mixed 
readily.  They  also  change  in  weight  rapidly  in  the  air.  It  is 
therefore  standard  practice  to  air-dry  the  sample.  This  may  be 
accomplished  by  spreading  in  a  thin  layer  in  a  tin  pan  placed  in 
a  warm  room  for  twenty-four  hours  or  longer  if  necessary  to 
bring  it  to  approximately  constant  weight.  The  process  may  be 
hastened  by  placing  the  samples  in  an  oven  such  as  is  used 
at  the  Bureau  of  Mines1  which  is  heated  to  not  over  100°  F.  and 
wh  ch  is  provided  with  forced  ventilation.  In  this  oven,  which  is 
illustrated  in  Fig.  41,  air  is  heated  by  a  Bunsen  burner  and  circu- 
lated by  a  small  electric  fan.  The  loss  in  weight  during  this 
process  is  reported  as  air-drying  loss.  All  analyses  are  made  on 
this  air-dried  coal  since  it  may  be  weighed  and  handled  in  the  air 
with  relatively  slight  change  of  weight.  There  is  evidence  that 
the  coal  slowly  changes  in  this  air-drying  process,  so  that  it  should 
not  be  exposed  to  the  air  longer  than  necessary.  Porter2  reports 
that  Pittsburg  coal  on  drying  eight  days  at  35°  C.  absorbed  0.17 
per  cent,  of  oxygen  and  that  a  Wyoming  coal  similarly  treated 
absorbed  0.70  per  cent. 

1  Technical  Paper  8,  Bureau  of  Mines,  1912. 

2  Jour.  Ind.  and  Eng.  Chem.,  5,  520  (1913). 


196 


GAS  AND  FUEL  ANALYSIS 


5.  Grinding  and  Preserving  the  Sample  for  Analysis. — The 
sample  of  coal  which  has  been  air-dried  or  is  at  least  so  nearly 
air-dry  that  it  does  not  change  in  weight  in  the  air  rapidly  is  to 
be  crushed  and  subdivided  until  a  portion  of  50  or  60  grm.  is 
obtained  from  which  a  sample  of  1  grm.  may  be  taken  which 


t* 


27 


FIG.  41. — Oven  for  air-drying  coal  samples. 

shall  be  representative  of  the  whole  original  mass  of  coal.  Bailey 
in  the  reference  quoted  in  the  preceding  chapter  gives  the  follow- 
ing rules  for  subdivision  in  the  laboratory. 


Size  of  coal  mesh 


Should  not  be  divided  to 
less  than 


2 

4 

8 

10 

20 


8300  grm. 

1100  grm. 

120  grm. 

55  grm. 

3  grm. 


THE  CHEMICAL  ANALYSIS  OF  COAL  197 

He  recommends  that  as  soon  as  the  sample  has  been  put  through 
an  8-mesh  sieve  that  it  be  all  crushed  to  60-mesh  or  finer. 

The  crushing  to  12-mesh  may  be  done  by  hand  in  a  mortar  or 
in  any  type  of  crusher  without 'much  danger  of  injuring  the 
sample  if  it  is  done  rapidly.  It  is  necessary  to  take  precautions, 
however,  to  prevent  injury  to  the  sample  during  fine  grinding, 
for  finely  ground  coal  absorbs  oxygen  from  the  air  rapidly  and 
gives  off  water.  The  exact  nature  of  this  reaction  is  not  un- 
derstood but  it  is  known  to  sensibly  affect  the  heating  value. 
This  change  is  accelerated  if  the  sample  becomes  heated  during 
the  fine  grinding.  For  this  reason  disc  grinders  should  be  used 
with  great  caution.  They  grind  rapidly  but  the  plates  get  hot, 
sometimes  hot  enough  to  start  destructive  distillation  of  the 
coal,  which  manifests  itself  by  a  tarry  odor.  If  the  disc  grinder 
is  used  the  plates  must  not  be  set  closer  than  necessary  and  the 
coal  must  be  fed  very  slowly.  The  best  method  of  finely 
grinding  coal  is  to  use  a  jar  mill.  This  consists  of  a  heavy 
porcelain  jar  provided  with  a  cover  which  may  be  clamped 
tight  on  a  rubber  gasket.  It  is  filled  about  one-third  full  of 
round  flint  pebbles  or  porcelain  balls  and  is  placed  in  a  frame 
where  it  may  be  rotated  at  the  rate  of  50  to  75  revolutions 
per  minute.  The  balls  tumbling  over  each  other  fall  with  suffi- 
cient force  to  crack  the  small  pieces  of  coal,  but  are  themselves 
worn  off  to  only  a  negligible  extent.  The  longer  the  coal  is 
left  in  the  jar  the  finer  it  becomes  and  it  is  easy  to  get  any  desired 
degree  of  fineness.  The  size  of  the  jar  required  and  the  diameter 
of  the  pebbles  will  vary  with  the  hardness  of  the  material  and  the 
size  of  the  lumps.  If  the  lumps  have  a  diameter  even  as  great  as 
one-fourth  that  of  the  pebbles,  some  of  the  lumps  may  become 
simply  rounded  balls  themselves  and  not  be  crushed  by  the  im- 
pact of  the  pebbles.  If  the  coal  has  been  put  through  a  10-  or  12- 
mesh  sieve  before  going  into  the  ball  mill  a  jar  of  8  in.  internal 
diameter  and  with  pebbles  3/4  in.  or  1  in.  in  diameter  will  grind 
the  sample  properly,  provided  the  coal  does  not  occupy  over  one- 
sixth  of  the  volume  of  the  jar.  When  the  grinding  is  completed 
the  jar  is  emptied  onto  a  coarse  sieve  which  retains  the  balls. 
The  coal  should  be  tested  on  a  60-mesh  sieve  and  any  portions 
failing  to  pass  it  should  be  separately  ground  to  pass  an  80-mesh 
sieve  and  added  to  the  main  portion.  These  coarse  particles 


198  GAS  AND  FUEL  ANALYSIS 

are  liable  to  be  slate  or  pyrites  and  therefore  especial  care  must 
be  taken  to  see  that  they  are  finely  ground  and  mixed  with  the 
main  sample.'  A  coal  ground  to  pass  a  60-mesh  sieve  is  fine 
enough  to  make  a  1-grm.  sample  as  representative  of  the  lot  as 
the  various  intermediate  samples  were  of  the  initial  sample.  It 
is  not  desirable  to  grind  the  coal  much  finer  because  of  the 
increased  error  due  to  loss  of  moisture  and  absorption  of  oxygen 
by  the  finely  powdered  coal. 

This  finely  ground  sample  may  now  be  stored  as  a  whole  in 
a  fruit  jar  or  subdivided  and  an  amount  of  only  50  grm.  placed 
in  a  wide-mouthed  bottle  closed  with  a  rubber  stopper.  The 
bottle  should  be  filled  only  half  full  so  that  the  analyst  before 
weighing  out  his  sample  may  gently  shake  and  rotate  the  bottle 
to  mix  the  contents.  Pyrites  and  slate  tend  to  work  to  the 
bottom  of  a  sample  bottle  and  the  precaution  of  mixing  before 
taking  a  sample  should  never  be  omitted. 

Even  the  most  carefully  preserved  coals  deteriorate  in  time. 
Parr1  has  shown  that  in  three  years'  storage  in  the  laboratory 
Eastern  coals  lose  in  heating  value  to  the  extent  of  0.5  to  1.5 
per  cent.,  while  Illinois  coals  deteriorate  to  the  extent  of  3  to  5 
per  cent.  Coals  which  are  to  be  kept  for  a  long  period  should 
be  sealed  as  nearly  air-tight  as  possible. 

6.  Moisture. — The  determination  of  moisture  in  coals  is 
complicated  by  the  change  which  the  coal  substance  'tself 
undergoes  when  subjected  to  heat  and  exposure  to  the  air. 
The  method  recommended  by  the  committee  of  the  American 
Chemical  Society  in  1899  prescribes  that  1  grm.  of  the  coal 
shall  be  dried  in  an  open  porcelain  or  platinum  crucible  at 
104-107°  C.  for  one  hour  and  shall  then  be  cooied  in  a  desiccator 
and  weighed  covered. 

The  errors  in  the  determination  of  moisture  in  coal  have  been 
studied  by  several  investigators,  among  them  Hillebrand  and 
Badger2  at  the  Bureau  of  Standards.  They  conclude  that  the 
most  nearly  correct  results  may  be  obtained  by  drying  in  vacuo 
over  concentrated  sulphuric  acid  for  a  period  of  two  days  or 
more.  The  method  prescribed  above  of  heating  for  one  hour 
in  a  closed  oven  at  105°-110°  C.  showed  the  moisture  to  be 

1  Eighth  Internat.  Congr.  Appl.  Chem.,  10,  225  (1912). 

2  Eighth  Internat.  Congr.  Appl.  Chem.,  10,  187.  (1912). 


THE  CHEMICAL  ANALYSIS  OF  COAL  199 

roughly  nine-tenths  as  great  as  that  obtained  by  the  vacuum 
method  when  the  comparisons  were  made  on  coals  which  had 
not  been  unduly  weathered.  If  the  heating  in  the  oven  was 
prolonged  an  hour  longer  the  apparent  moisture  rose  somewhat, 
but  was  still  below  that  obtained  by  the  vacuum  method.  If 
the  coal  was  heated  for  one  hour  in  an  oven  through  which 
dry  air  was  circulated,  the  results  obtained  were  much  more 
consistent  and  in  most  cases  approached  quite  closely  those 
obtained  in  a  vacuum. 

The  method  adopted  as  standard  by  the  U.  S.  Bureau  of 
Mines,  as  given  in  their  Technical  Paper  8,  is  to  take  a  1-grm. 
sample  of  the  60-mesh  coal,  place  it  in  a  weighed  7/8  in.  by  1  3/4 
in.  porcelain  crucible  and  heat  for  an  hour  at  105°  C.  in  a  constant  . 
temperature  oven  in  a  stream  of  dry  air.  The  crucible  is  then 
removed  from  the  oven,  covered  and  cooled  in  a  desiccator 
over  sulphuric  acid.  The  loss  in  weight  multiplied  by  100 
is  counted  as  the  percentage  of  moisture.  The  oven  which  they 
use  is  of  copper  with  double  walls.  The  space  between  the 
inner  and  outer  wall  is  filled  with  a  solution  of  approximately 
45  parts  by  weight  of  glycerine  and  55  of  water,  the  exact 
proportions  being  modified  to  get  a  solution  boiling  at  105°  C. 
A  reflux  condenser  prevents  change  in  boiling-point  through 
evaporation  of  the  water.  A  current  of  air  dried  by  passing 
through  sulphuric  acid  and  preheated  by  passing  through  a 
copper  spiral  immersed  in  the  glycerine  is  forced  into  the  drying 
chamber  at  the  back  and  escapes  through  a  small  hole  in  the 
door.  The  air  is  blown  in  at  a  rate  sufficient  to  change  the 
volume  of  air  in  the  oven  from  8  to  10  times  an  hour. 

The  1913  report  of  the  Committee  on  Coal  Analysis  recom- 
mends that  the  sample  of  approximately  1  grm.  be  weighed 
into  a  pair  of  shallow  weighing  capsules  with  ground  caps. 
For  anthracite  and  bituminous  coals  the  capsules  are  to  be 
placed  open  in  a  preheated  oven  at  104-110°  C.,  through  which 
passes  a  current  of  air  dried  by  concentrated  sulphuric  acid. 
After  being  heated  for  one  hour  in  this  oven  the  capsules  are 
to  be  removed,  covered  at  once  and  cooled  in  a  desiccator  con- 
taining concentrated  sulphuric  acid.  Sub-bituminous  and  lig- 
nitic  coals  are  to  be  dried  in  a  stream  of  dry  carbon  dioxide  or 
nitrogen.  After  the  samples  are  dried  they  are  to  be  placed  in  a 


200  GAS  AND  FUEL  ANALYSIS 

vacuum  desiccator  which  is  then  exhausted  to  remove  absorbed 
carbon  dioxide.  After  exhaustion  the  desiccator  is  refilled  with 
dry  air. 

7.  Volatile  Matter. — There  can  never  be  an  absolute  method 
for  the  determination  of  volatile  matter,  for  only  a  very  small 
proportion  of  the  material  evolved  from  coal  at  a  red  heat 
was  present  as  such  in  the  coal.  Most  of  this  volatile  ma- 
terial is  a  decomposition  product  whose  amount  varies  with 
the  rate  of  heating,  the  maximum  temperature  attained,  the 
character  of  the  flame,  the  size  of  the  crucible  and  other  condi- 
tions. It  is  necessary,  therefore,  in  a  standard  method  to 
fix  every  possible  variable  as  rigidly  as  possible. 

The  1899  method  of  the  American  Chemical  Society  is  as 
follows: 

"Place  1  grm.  of  fresh,  undried,  powdered  coal  in  a  platinum  cruci- 
ble, weighing  20  or  30  grm.  and  having  a  tightly  fitting  cover.  Heat 
over  the  full  flame  of  a  Bunsen  burner  for  seven  minutes.  The  cruci- 
ble should  be  supported  on  a  platinum  triangle  with  the  bottom  six  to 
eight  centimeters  above  the  top  of  the  burner.  The  flame  should  be 
fully  twenty  centimeters  high  when  burning  free,  and  the  determina- 
tion should  be  made  in  a  place  free  from  draughts.  The  upper  surface 
should  remain  covered  with  carbon.  To  find  'Volatile  Combustible 
Matter'  substract  the  per  cent,  of  moisture  from  the  loss  found  here." 

More  recent  investigations  especially  by  Fieldner  and  Davis1 
and  by  Parr2  have  thrown  some  light  on  the  causes  of  variation. 
The  former  authors  working  in  the  laboratories  of  the  U.  S. 
Bureau  of  Mines  at  Pittsburgh  and  Washington  found  that  the 
carburetted  water  gas  of  Washington  gave  a  maximum  tempera- 
ture of  970°  C.  within  the  crucible  which  was  120°  hotter  than 
could  be  obtained  with  the  coal  gas  of  Pittsburgh  or  with  natural 
gas  burned  under  favorable  conditions.  They  summarize  the 
results  of  their  experiments  as  follows : 

"Two  laboratories  are  likely  to  vary  2  per  cent,  in  volatile  matter, 
both  using  the  official  method  (of  1899).  The  percentage  of  volatile 
matter  obtained  from  the  same  sample  of  coal  varies  with  the  tem- 
perature and  rate  of  heating.  This  is  not  sufficiently  defined  by  height 

1  Jour.  Ind.  andJSng.  Chem.,  2,  304  (1910). 

2  Jour.  Ind.  andEng.  Chem.,  3,  900  (1911). 


THE  CHEMICAL  ANALYSIS  OF  COAL  201 

of  flame.  Temperatures  ranging  from  760°  C.  to  890°  C.  may  be  at- 
tained with  a  20-cm.  natural  gas  flame,  when  the  gas  pressure  is  varied 
from  1  to  13  in.  of  water;  variations  of  2  per  cent,  volatile  matter  are 
thus  produced.  Differences  in  type^nd  sizes  of  burner  influence  re- 
sults from  0.3  to  1.5  per  cent.  Polished  crucibles  become  hotter  and 
yield  about  1  per  cent,  more  volatile  matter  than  dull  gray  ones.  Labo- 
ratories using  natural  gas  are  apt  to  get  results  on  volatile  matter  that 
are  considerably  lower  than  those  using  coal  gas,  unless  the  following 
precautions  are  observed:  (1)  Gas  should  be  supplied  to  the  burner 
at  a  pressure  of  not  less  than  10  in.  of  water.  (2)  Natural  gas  burners 
admitting  an  ample  supply  of  air  should  be  used.  (3)  Gas  and  air 
should  be  regulated  so  that  a  flame  with  a  short,  well-defined  inner 
cone  is  produced.  (4)  The  crucibles  should  be  supported  on  platinum 
triangles  and  kept  in  well-polished  condition." 

The  1913  report  of  the  Committee  on  Coal  Analysis  recom- 
mends the  following  two  alternate  methods  for  the  determination 
of  volatile  matter. 

"It  is  recommended  that  for  volatile  matter  determinations  a  10- 
grm.  platinum  crucible  be  used  having  a  capsule  cover,  that  is,  one  which 
fits  inside  of  the  crucible  and  not  on  top.  The  crucible  with  1  grm.  of 
coal  is  placed  in  a  muffle  maintained  at  approximately  950°  C.  for  seven 
minutes.  With  a  muffle  of  the  horizontal  type,  the  crucible  should  not 
rest  on  the  floor  of  the  muffle  but  should  be  supported  on  a  platinum 
or  nichrome  triangle  bent  into  a  tripod  form.  After  the  more  rapid 
discharge  of  the  volatile  matter,  well  shown  by  the  disappearance  of 
the  luminous  flame,  the  cover  should  be  tapped  lightly  to  more  per- 
fectly seal  the  cover  and  thus  guard  against  the  admission  of  air. 

"  One  gram  of  coal  is  placed  in  a  platinum  crucible  of  approximately 
20  c.c.  capacity  (35  mm.  in  diameter  at  the  top  and  35  mm.  high). 
The  crucible  should  have  a  capsule  cover  which  will  readily  adjust 
itself  to  the  inside  upper  surface  of  the  crucible.  The  crucible  is  placed 
in  the  flame  of  a  Meker  burner,  size  No.  4,  having  approximately  an 
outside  diameter  at  the  top  of  25  mm.  and  giving  a  flame  not  less  than 
15  cm.  high.  The  temperature  should  be  from  900°  to  950°  C.  de- 
termined by  placing  a  thermocouple  through  the  perforated  cover  which 
for  this  purpose  may  be  of  nickel.  The  junction  of  the  couple  should 
be  placed  in  contact  with  the  center  of  the  bottom  of  the  crucible. 
Or  the  temperature  may  be  indicated  by  the  fusion  of  pure  potassium 
chromate  in  the  covered  crucible  (fusion  of  K2Cr04,  940°  C.).  The 
crucible  is  placed  in  the  flame  about  1  cm.  above  the  top  of  the  burner 
and  the  heating  is  continued  for  seven  minutes.  After  the  main  part 


202  GAS  AND  FUEL  ANALYSIS 

of  the  gases  have  been  discharged  the  cover  should  be  tapped  into  place 
as  above  described. 

"For  lignites  a  preliminary  heating  of  five  minutes  is  carried  out, 
during  which  time  the  flame  of  the  burner  is  played  upon  the  bottom 
of  the  crucible  in  such  a  manner  as  to  bring  about  the  discharge  of  vola- 
tile matter  at  a  rate  not  sufficient  to  cause  sparking.  After  the  pre- 
liminary heating  the  crucible  is  placed  in  the  full  burner  flame  for 
seven  minutes  as  above  described." 

8.  Ash. — The  ash  of  coal  is  generally  defined  as  the  mineral 
residue  remaining  after  complete  combustion.  The  1899  method 
of  the  American  Chemical  Society  is  as  follows : 

"Burn  the  portion  of  powdered  coal  used  for  the  determination  of 
moisture,  at  first  over  a  very  low  flame,  with  the  crucible  open  and  in- 
clined, till  free  from  carbon.  If  properly  treated,  this  sample  can  be 
burned  much  more  quickly  than  the  dense  carbon  left  from  the  de- 
termination of  volatile  matter.  It  is  advisable  to  examine  the  ash  for 
unburned  carbon  by  moistening  it  with  alcohol." 

The  errors  attending  the  determination  of  ash  have  been 
studied  very  carefully  by  Parr1,  who  has  shown  that  90  per  cent, 
of  the  Illinois  coals  carry  as  much  as  0.2  per  cent,  of  calcium  car- 
bonate, nearly  half  have  more  than  1  per  cent.,  one-fifth  have 
more  than  2  per  cent.,  a  considerable  number  over  4  per  cent., 
and  a  few  isolated  cases  carry  over  10  per  cent,  of  calcium  car- 
bonate in  the  raw  coal.  Since  decomposition  of  CaCOs  is  rapid 
at  900°  C.  and  evident  at  600°  it  is  apparent  that  in  coals  of  this 
type  care  must  be  taken  to  determine  the  actual  amount  of 
CaCOs  present.  Parr  has  also  shown  that  sulphate  in  the  form 
of  ferrous  or  ferric  sulphate  is  present  in  fresh  coal  in  amounts 
varying  from  a  few  tenths  up  to  1  per  cent,  and  that  this  amount 
increases  rapidly  in  the  finely  ground  portions  of  the  laboratory 
sample.  With  coals  high  in  lime  this  sulphate  on  ignition  for 
ash  probably  becomes  calcium  sulphate,  as  does  also  the  sulphur 
of  pyrites. 

The  1913  report  of  the  Committee  on  Coal  Analysis  recom- 
mends the  following  method  for  the  determination  of  ash. 

1  Jour.  Ind.  and  Eng.  Chem.,  5,  523  (1913).  111.  State  Geological  Survey, 
Bui.  16,  p.  242. 


THE  CHEMICAL  ANALYSIS  OF  COAL  203 

"Unless  the  coal  is  of  a  type  known  to  be  free  from  carbonate  the 
amount  of  carbon  dioxide  must  be  determined.  A  5-grm.  sample, 
recently  boiled  distilled  water  and  dilute  hydrochloric  acid  are  em- 
ployed, making  use  of  any  convenient  apparatus  for  collecting,  absorb- 
ing and  measuring  accurately  the  carbon  dioxide  discharged  from  the 
coal.  It  is  most  convenient  to  obtain  the  factor  as  in  the  form  of 
carbon. 

"One  gram  of  coal,  either  freshly  weighed  or  that  which  has  been  used 
for  the  moisture  determination,  is  ignited  in  a  shallow  capsule  or  porce- 
lain crucible  by  placing  directly  in  a  muffle  maintained  at  a  dull  or 
cherry-red  temperature  between  700  and  750°  C.  and  retained  at  this 
temperature  for  20  or  30  minutes  or  until  all  of  the  carbon  is  burned  out. 
The  capsule  is  cooled  in  a  desiccator  and  weighed.  In  the  absence  of  a 
muffle  the  desired  temperature  may  be  obtained  by  placing  the  capsule 
at  first  just  above  the  tip  of  a  Bunsen  flame  turned  down  to  about  2 
or  3  in.  in  height.  After  the  larger  part  of  the  carbon  is  burned  off  in 
this  manner  the  flame  is  increased  so  that  the  tip  comes  well  into 
contact  with  the  bottom  of  the  capsule. 

"For  coals  having  carbon  dioxide  present  in  an  amount  to  exceed  0.2 
per  cent.,  the  ash  after  cooling  is  moistened  with  a  few  drops  of  sulphuric 
acid  (diluted  1  : 1)  and  again  carefully  brought  up  to  750°  C.  and  re- 
tained at  that  temperature  for  three  to  five  minutes.  The  capsule  is 
cooled  in  a  desicator  and  weighed.  Three  times  the  equivalent  of 
carbon  present  as  carbon  dioxide  is  subtracted  from  the  ash  as  weighed 
in  order  to  restore  the  weight  of  the  calcium  sulphate  formed  to  the 
equivalent  of  calcium  carbonate." 

The  appearance  of  the  ash  gives  some  indication  of  its  fusing 
point  and  hence  its  tendency  to  form  clinkers.  The  largest  con- 
stituents in  ash  are  silica  and  alumina,  all  of  whose  compounds 
have  relatively  high  melting-point  and  are  white  in  color.  Iron 
oxide  colors  ash  red  and  reduces  the  melting-point  of  the  alumina 
silica  series  markedly.  Therefore  a  red  ash  indicates  low  melting- 
point  and  trouble  with  clinker  while  a  white  ash  indicates  high 
melting-point.  This  rule  fails  with  coals  such  as  those  from 
Illinois  which  carry  material  amounts  of  lime,  for  the  lime  reduces 
the  melting-point  without  giving  a  color.  However,  the  Illinois 
coals  usually  carry  enough  iron  to  give  a  red  color  as  well. 

9.  Fixed  Carbon. — Fixed  carbon  is  obtained  by  adding  together 
the  weights  of  moisture,  volatile  matter  and  ash  and  subtracting 
this  sum  from  the  weight  of  the  initial  sample.  Since  the  amount 


204  ;        GAS  AND  FUEL  ANALYSIS 

of  fixed  carbon  is  obtained  by  difference,  proximate  analyses  of 
coal  always  add  up  to  an  even  100  per  cent.  The  percentage 
of  fixed  carbon  plus  ash  gives  a  fair  indication  of  the  amount  of 
coke  which  would  be  obtained  from  a  coal.  An  indication  of  the 
quality  of  the  coke  may  be  obtained  from  an  examination  of  the 
residue  remaining  after  the  determination  of  volatile  matter. 
Good  coking  coals  give  a  button  of  hard  dense  coke.  Feebly 
coking  coals  give  a  cracked  and  weak  button  while  non-coking 
anthracites  and  lignites  give  a  powdery  or  granular  residue. 

10.  Sulphur. — The  estimation  of  sulphur  is  usually  considered 
as  part  of  a  proximate  analysis  although  it  is  estimated  separately 
and  its  percentage  is  not  included  in  the  100  per  cent,  formed  by 
the  sum  of  the  moisture,  volatile  matter,  fixed  carbon  and  ash. 
Sulphur  usually  exists  in  coal  as  pyrites  FeS2,  but  part  of  it  may 
exist  in  combination  with  carbon  compounds,  part  even  as  free 
sulphur  and  especially  in  weathered  coals  as  calcium  sulphate 
or  sulphate  of  iron.  No  attempt  is  ordinarily  made  to  distinguish 
between  these  various  forms  of  sulphur.  The  coal  is  treated 
with  an  agent  which  finally  brings  all  forms  of  sulphur  into  a 
soluble  sulphate  form.  This  is  then  precipitated  as  barium  sul- 
phate and  calculated  back  to  sulphur.  The  method  recommended 
in  1899  by  the  American  Chemical  Society  was  a  modification  of 
that  proposed  by  Eschka  in  1874. 

The  committee  on  Coal  Analysis  in  its  1913  recommendations 
adopts  the  report  presented  by  Barker  permitting  the  use  of  three 
alternative  methods  which  have  shown  themselves  to  be  accurate. 
The  methods  are: 

(a)  the  Eschka  method. 

(6)  the  Atkinson  method  of  fusion  with  sodium  carbonate. 

(c)  the  method  of  fusion  with  sodium  peroxide. 
The  Eschka  method  is  recommended  in  substantially  the  same 
form  as  in  the  standard  method  of  1899.  The  substitution  of 
copper  oxide  for  magnesium  oxide  in  the  method  gives  more 
rapid  combustion  but  it  has  been  objected  to  on  the  ground  that 
the  black  specks  of  copper  oxide  look  so  much  like  free  carbon 
that  it  is  difficulty  to  tell  when  the  coal  is  completely  burned. 
The  following  details  of  the  Eschka  method  are  from  the 
Committee's  report. 

1  Jour.  Ind.  and  Eng.  Chem.,  5,  524  (1913). 


THE  CHEMICAL  ANALYSIS  OF  COAL  205 

"The  Eschka  Method. — The  essentials  of  this  method  as  described 
by  G.  L.  Heath1  have  been  modified  as  given  in  the  former  report  of 
the  Committee  of  the  American  Chemical  Society  on  Coal  Analysis.2 
Additional  directions  for  application  when  city  gas  is  used  are  also 
included  in  the  method  herein  recommended. 

"  Thoroughly  mix  on  glazed  paper  1.3737  grm.  of  coal  and  6  grm. 
of  Eschka  mixture.  This  mixture  is  prepared  by  thoroughly  incopor- 
ating  two  parts  magnesium  oxide  with  one  part  of  sodium  carbonate 
by  passing  through  a  40-mesh  screen.  By  this  method  of  preparation 
the  mixture  attains  a  uniformity  comparable  with  that  of  the  labo- 
ratory sample  of  coal  and  thorough  incorporation  is,  therefore,  more 
easily  effected.  Transfer  to  a  No.  1  Royal  Berlin  porcelain  crucible 
and  cover  with  about  two  grams  of  the  Eschka  mixture.  On  account 
of  the  amount  of  sulphur  contained  in  artificial  gas,  it  is  preferable 
to  heat  the  crucible  over  an  alcohol,  gasoline  or  natural  gas  flame  or  in 
an  electrically  heated  muffle.  Heat  the  crucible,  placed  in  a  slanting 
position  on  a  triangle,  over  a  very  low  flame  to  avoid  rapid  expulsion 
of  the  volatile  matter,  which  tends  to  prevent  complete  absorption  of 
the  products  of  combustion  of  sulphur.  Heat  the  crucible  slowly  for 
about  30  minutes,  gradually  increasing  the  temperature  and  occasionally 
stirring  until  all  black  particles  disappear,  which  is  an  indication  of  the 
completeness  of  the  procedure. 

"The  use  of  artificial  gas  for  heating  the  coal  and  Eschka  mixture 
is  permissible,  provided  the  crucibles  are  heated  in  a  muffle  and  a  blank 
determination  of  the  amount  of  sulphur  absorbed  from  the  gas  is  made. 
Place  a  crucible  in  a  cold  gas  muffle  and  gradually  raise  the  temperature 
to  about  870°  or  925°  C.  (cherry-red  heat)  in  about  one  hour.  Main- 
tain this  maximum  temperature  for  about  one  and  a  half  hours  and 
then  allow  the  crucible  to  cool  in  the  muffle.  Remove  and  empty  the 
contents  into  a  300  c.c.  beaker  and  digest  with  200  c.c.  of  hot  water 
for  one-half  to  three-quarters  of  an  hour,  with  occasional  stirring. 
Filter  and  wash  the  insoluble  matter  by  decantation.  After  several 
washings  in  this  manner,  transfer  the  insoluble  matter  to  the  filter  and 
wash  five  times,  keeping  the  mixture  well  agitated.  Treat  the  filtrate 
amounting  to  about  250  c.c.  with  10  to  20  c.c.  of  saturated  bromine 
water  and  make  slightly  acid  with  concentrated  hydrochloric  acid. 
Transfer  the  beakers  to  the  hot  plate  and,  upon  boiling,  precipitate 
the  soluble  sulphates  by  adding  slowly  from  a  pipet  with  constant  stir- 
ring 10  c.c.  of  a  hot  10  per  cent,  solution  of  barium  chloride.  Continue 
boiling  for  fifteen  minutes  and  allow  to  stand  for  at  least  two  hours 

1  /.  Am.  Chem.  Soc.,  20,  630. 

2  Ibid.,  21,  1127. 


206  GAS  AND  FUEL  ANALYSIS 

at  a  temperature  just  below  boiling.  Filter  through  an  ashless  filter 
paper  and  wash  first  with  hot  water  containing  1  c.c.  of  hydrochloric 
acid  per  liter  and  then  with  hot  distilled  water  until  a  silver  nitrate 
solution  shows  no  precipitate  with  a  drop  of  the  filtrate.  Place  the 
wet  filter  containing  the  precipitate  of  barium  sulphate  in  a  weighed 
platinum  or  alundum  crucible,  allowing  a  free  access  of  air  by  folding 
the  paper  over  the  precipitate  loosely  to  prevent  spattering.  The  paper 
should  be  smoked  off  gradually  at  first.  After  the  paper  is  practically 
consumed  raise  the  temperature  to  approximately  925°  C.  and  heat  to 
constant  weight.  In  case  artificial  gas  is  used  as  a  heating  agent,  a 
blank  to  correct  for  contamination  due  to  sulphur  in  the  gas  is  carried 
through  the  process  in  the  manner  described  above,  using  the  same 
amounts  of  Eschka  mixture,  wash  water,  bromine  water,  hydrochloric 
acid  and  barium  chloride  solution  as  employed  in  the  regular  determina- 
tion. A  large  number  of  tests  using  a  mixed  coal  and  carburetted 
water  gas  containing  not  more  than  25  grains  of  sulphur  per  100  cu.  ft. 
show  blanks  averaging  0.003  grm.  of  barium  sulphate.  These  blanks 
include  the  impurities  in  the  form  of  sulphur  compounds  in  the  reagents, 
which  amount  to  nearly  one-half  of  the  total  weights.  The  percentage 
of  sulphur  is  obtained  by  deducting  the  blank,  provided  artificial  gas 
is  used,  and  multiplying  the  resulting  figures  by  10." 

The  Peroxide  Fusion  Method. — The  decomposition  of  coal 
by  fusion  with  sodium  peroxide  was  first  proposed  by  Parr1 
for  calorimetric  purposes.  The  reaction  was  adapted  to  the  esti- 
mation of  sulphur  by  Sundstrom2  and  later  modified  by  Pennock 
and  Morton3,  and  Parr4.  The  method  is  entirely  reliable  and 
is  much  more  rapid  than  the  Eschka  method. 

When  a  mixture  of  a  dry  combustible  substance  and  sodium 
peroxide  in  proper  proportions  is  ignited  by  a  hot  iron  wire,  the 
mass  fuses  with  very  little  spattering  and  the  sulphur,  no  matter 
what  its  initial  form  of  combination,  is  converted  to  a  soluble 
sodium  sulphate.  If  the  coal  is  damp  or  the  proportions  are  not 
correct  there  may  be  violent  spattering  so  the  reaction  should 
be  carried  out  in  a  closed  vessel.  The  residue  from  the  deter- 
mination of  heating  value  in  the  Parr  calorimeter  is  of  course 
available  at  once  for  the  estimation  of  sulphur.  Where  a  separate 

1  J.  Am.  Chem.  Soc.,  22,  646  (1900). 

2  J.  Am.  Chem.  Soc.,  25,  184  (1903). 

3  J.  Am.  Chem.  Soc.  25,  1265  (1903). 

4  J.  Am.  Chem.  Soc.,  30,  767  (1908). 


THE  CHEMICAL  ANALYSIS  OF  COAL 


207 


combustion  for  sulphur  is  to  be  made  a  simple  crucible  of  steel  or 
brass  provided  with  a  perforated  cover  which  may  be  clamped  in 
place  is  used,  as  shown  in  Fig.  42.  For  a  charge  of  0.7  grm. 
bituminous  coal  about  16  grm.  of  sodium  peroxide  are  required 
while  for  the  same  weight  of  coke  or  anthracite  about  12  grm.  of 
peroxide  are  best.  The  charge  is  mixed,  the  cover  clamped  on 
and  the  crucible  placed  on  a  support  in  a  pan  of  water,  so  that 
its  lower  half  is  immersed  and  yet  there  is  free  circulation  of  water 
around  the  bottom.  The  charge  is  fired  by  a  stiff  iron  wire  which 
is  heated  to  redness  and  thrust 
through  the  hole  in  the  cover.  If  the 
reaction  proceeds  properly  almost  no 
flame  will  issue  from  the  hole.  If  the 
proportions  are  not  correct  there  may 
be  considerable  spattering  so  that  the 
operator  should  stand  at  arms  length 
from  the  crucible  when  inserting  the 
wire.  If  the  first  explosion  is  too  vio- 
lent, add  more  sodium  peroxide  which 
acts  as  a  diluent.  If,  on  the  other 
hand,  combustion  has  been  incomplete 
as  shown  by  soot  on  the  inside  of  the 
lid  of  the  crucible,  decrease  the  amount 
of  sodium  peroxide  on  the  next  at- 
tempt. If  there  is  difficulty  in  ob- 
taining ignition  as  is  sometimes  the  case  with  coke  and  especially 
with  ashes,  add  an  accelerator.  Parr  recommends  the  following 
fusion  mixture:  10  grm.  sodium  peroxide,  0.5  grm.  potassium 
chlorate,  0.5  grm.  benzoic  acid. 

To  dissolve  the  fused  mass,  place  the  crucible  and  cover 
in  about  200  c.c.  of  distilled  water.  Rinse  off  the  crucible, 
acidify  slightly  with  HC1,  filter  out  any  insoluble  matter  and 
proceed  with  precipitation  of  BaSC>4  as  in  the  Eschka  method. 

The  details  of  the  Atkinson  method  as  recommended  by  the 
Committee  on  Coal  Analysis  are  as  follows: 

The  Atkinson  Method.1 — "Thoroughly  mix  on  glazed  paper  1  grm.  of 
the  laboratory  sample  of  coal  with  7  grm.  of  dry  sodium  carbonate 
and  spread  evenly  over  the  bottom  of  a  shallow  platinum  or  porcelain 

1  J.  Am.  Chem.  Soc.,  21,  1128  (1899). 


FIG.  42.— Crucible  for 
peroxide  fusion. 


208  GAS  AND  FUEL  ANALYSIS 

dish.  Place  on  a  triangle  slightly  elevated  above  the  bottom  of  a  cold 
muffle.  Raise  the  temperature  of  the  muffle  gradually  until  a  tem- 
perature of  650°  to  700°  C.  (dull  red  heat)  has  been  obtained  in  half 
an  hour  and  maintain  this  temperature  for  ten  or  fifteen  minutes. 
The  sodium  carbonate  should  not  sinter  or  fuse.  The  mixture  should 
not  be  stirred  during  the  heating  process.  When  the  dish  has  cooled 
sufficiently  to  handle,  the  matter  should  be  examined  for  black  particles 
of  unburned  carbon  and  in  case  such  indications  of  incompleteness  of 
the  process  appear,  the  dish  should  be  replaced  and  heated  for  a  short 
time.  When  all  carbon  is  burned,  remove  the  dish  and  digest  the  con- 
tents with  100  to  125  c.c.  of  warm  water.  Allow  the  insoluble  matter 
to  settle,  decant  through  a  filter  and  wash  several  times  by  decantation. 
Transfer  to  the  filter,  adding  a  few  drops  of  a  solution  of  pure  sodium 
chloride,  if  the  insoluble  matter  tends  to  pass  through  the  filter.  The 
washing  should  be  continued  until  the  filtrate  shows  no  alkaline  reaction. 
Make  the  filtrate  slightly  acid  with  sufficient  concentrated  hydrochloric 
acid  and  precipitate  the  sulphates  with  barium  chloride  as  described 
under  the  Eschka  method.  No  oxidizing  agent  is  required." 

Sulphur  may  also  be  determined  in  the  water  rinsed  from 
the  bomb  calorimeter  after  a  calorimetric  determination,  pro- 
vided that  the  calorimeter  is  provided  with  a  lining  which 
is  not  attacked  by  the  acid  formed.  The  bomb  should  be 
very  thoroughly  rinsed  with  hot  water,  the  solution  filtered 
and  precipitated  with  BaCl2  as  usual.  The  tendency  with 
this  method  will  be  toward  low  results. 

Parr1  has  developed  a  rapid  photometric  method  for  the 
determination  of  sulphur  in  coal.  The  residue  from  the  fusion 
with  sodium  peroxide  is  dissolved,  acidified,  diluted,  and  pre- 
cipitated cold  with  a  mixture  of  barium  chloride  and  oxalic 
acid.  The  precipitated  barium  sulphate  is  in  a  very  finely 
divided  condition  so  that  it  does  not  settle  readily.  The 
photometer  consists  of  a  graduated  tube  of  special  design  which 
rests  upon  a  diaphragm  below  which  is  a  candle  flame.  The 
emulsion  of  BaSO4  and  solution  is  slowly  poured  into  this 
photometer  until  the  sharp  outline  of  the  flame  disappears. 
The  height  of  solution  in  the  photometer  tube  gives,  by  reference 
to  a  special  table,  the  per  cent,  of  sulphur  in  the  coal.  Results 

1  Jour.  Am.  Chem.  Soc.,  26,  1139  (1904);  Jour.  Ind.  and  Eng.  Chem.,  1, 
689  (1909). 


THE  CHEMICAL  ANALYSIS  OF  COAL  209 

on  35  coals  quoted  by  Parr  show  good  agreement  with  gravi- 
metric methods. 

11.  Ultimate  Analysis. — Carbon  and  Hydrogen. — Carbon  and 
hydrogen  in  coal  and  coke  are  determined  as  is  usual  in  the 
ultimate  analysis  of  organic  compounds,  by  combustion  in  a 
stream  of  dry  and  pure  oxygen  and  absorption  of  the  resulting 
carbon  dioxide  and  water.  The  analysis  is  a  difficult  one 
and  should  not  be  attempted  by  one  who  has  not  had  practice 
in  the  general  method.  If  it  is  necessary  for  an  analyst  without 
training  in  this  particular  line  to  undertake  such  an  analysis 
he  should  practice  on  the  ultimate  analysis  of  such  pure  com- 
pounds as  sugar  and  benzoic  acid  until  he  has  attained  proficiency. 
Detailed  directions  for  these  determinations  in  coal  are  given  in 
Technical  Paper  8  of  the  Bureau  of  Mines. 

In  a  determination  of  the  heating  value  of  coal  in  a  bomb 
calorimeter,  there  is  complete  oxidation  of  the  carbon  to  carbon 
dioxide  and  of  the  hydrogen  to  water.  An  absorption  train 
may  be  connected  to  the  bomb  and  the  gases  allowed  to  bubble 
slowly  through  it.  After  the  pressure  in  the  bomb  has  fallen 
to  that  of  the  atmosphere  the  bomb  may  be  immersed  in  a 
dish  of  hot  water  and  suction  applied  to  the  absorption  train. 
It  is  in  this  way  possible  to  estimate  the  carbon  dioxide  and 
water  formed  in  the  combustion.  Kroeker1  proposes  a  bomb 
which  has  an  inlet  and  an  outlet  valve  so  that  dry  and  pure 
air  may  be  passed  through  the  bomb  after  the  pressure  has 
been  relieved.  The  method  is  capable  of  giving  good  results 
in  skilled  hands.  Great  care  must  be  taken  to  keep  the  packing 
on  the  oxygen  valves  in  perfect  condition  as  otherwise  part 
of  the  products  of  combustion  will  escape  during  the  slow 
process  of  emptying  the  bomb.  There  is  also  a  minor  error 
due  to  the  oxidation  of  some  of  the  nitrogen  to  form  nitric  acid 
which  is  reported  as  carbon  dioxide. 

Parr2  has  proposed  a  gas  volumetric  method  of  determining 
carbon  from  the  residue  of  the  peroxide  fusion  in  the  Parr 
calorimeter.  The  residue  consisting  largely  of  Na2C03  and 
Na2O2  is  dissolved  in  water  and  treated  with  acid.  Carbon 
dioxide  and  oxygen  are  evolved  and  the  carbon  dioxide  is 

1  Zeit.  d.  Vereins  f.  d.  Riibenzuckerindustrie,  46,  177  (1896). 

2  University  of  Illinois  Bulletin  Vol.  1,  No.  20  (1904). 

14 


210  GAS  AND  FUEL  ANALYSIS 

estimated  by  absorption.  There  are  a  number  of  minor  sources 
of  error  which  make  it  difficult  to  get  accurate  results  by  this 
method.  Sodium  peroxide  both  dry  and  in  solution  readily 
absorbs  carbon  dioxide  from  the  air  and  care  is  necessary  in 
order  to  keep  the  correction  factors  constant.  Difficulty  has 
also  been  experienced  in  completely  boiling  off  the  carbon  dioxide 
from  the  solution. 

12.  Nitrogen. — The  chief  value  attaching  to  a  knowledge  of 
the  per  cent,  of  nitrogen  in  a  coal  is  the  indication  which  it  is  be- 
lieved to  give  of  the  amount  of  ammonia  which  the  coal  will 
yield  on  destructive  distillation.  No  attempt  is  usually  made  to 
distinguish  between  the  various  forms  in  which  nitrogen  may  exist 
in  coal.  The  total  nitrogen  is  best  determined  by  the  Kjehldahl 
method  or  one  of  its  modifications  as  regularly  used  in  the 
ultimate  analysis  of  organic  compounds.  The  following  de- 
tails are  taken  from  Techinical  Paper  8  of  the  Bureau  of  Mines. 


"The  well-known  Kjehldahl  method  is  used  in  determining  nitrogen. 
One  gram  of  the  coal  sample  is  boiled  with  30  c.c.  of  concentrated 
sulphuric  acid  (H2S04)  and  0.6  grm.  of  mercury  until  all  particles  of 
coal  are  oxidized  and  the  solution  nearly  colorless.  The  boiling  should 
be  continued  at  least  two  hours  after  the  solution  has  reached  the  straw- 
colored  stage;  then  crystals  of  potassium  permanganate  (KMn04)  are 
added,  a  few  at  a  time,  until  a  permanent  green  color  remains.  After 
cooling,  the  solution  is  diluted  to  about  200  c.c.  with  cold  water. 
Twenty-five  cubic  centimeters  of  potassium  sulphide  (K2S)  solution  (40 
grm.  K2S  per  liter)  are  added  to  precipitate  the  mercury;  to  prevent 
bumping  1.0  grm.  of  granular  zinc,  and,  to  prevent  frothing,  a  piece  of 
paraffine  about  the  size  of  a  brass  1  grm.  weight  are  also  added.  Enough 
saturated  sodium  hydroxide  (NaOH)  solution  (usually  80  to  100  c.c.)  to 
make  the  solution  distinctly  alkaline  is  next  added  and  the  flask  is  at 
once  connected  with  the  condenser.  The  ammonia  (NH)3  is  distilled 
over  into  a  measured  amount  of  standard  sulphuric  acid  solution,  to 
which  has  been  added  sufficient  cochineal  indicator  for  titration.  The 
solution  is  distilled  until  about  200  c.c.  of  distillate  has  passed  over,  and 
the  distillate  is  titrated  with  standard  ammonia  (NH4OH)  solution  (20 
c.c.  NH4OH  solution  =10  c.c.  H2S04  solution  =  0.05  grm.  nitrogen). 
The  transfer  to  a  distillation  flask  may  be  avoided  by  the  use  of  a  500 
c.c.  Kjehldahl  flask  for  digestion  of  the  coal,  connection  being  made 
direct  from  the  Kjeldahl  digestion  flask  to  the  condensing  apparatus." 


THE  CHEMICAL  ANALYSIS  OF  COAL  211 

13.  Phosphorus. — Phosphorus  is  usually  determined  only  in 
fuels  which  are  to  be  used  for  metallurgical  processes  where  the 
fuel  is  to  come  in  direct  contact  with  the  metal.     The  following 
details  are  those  of  the  Bureau  of  Mines. 

"For  the  determination  of  phosphorus  in  coal  or  coke,  a  sample 
weighing  6.52  grm.  is  burned  to  ash  in  the  muffle  furnace.  The  ash  is 
mixed  with  four  to  six  times  its  weight  of  sodium  carbonate  plus  0.2 
grm.  of  sodium  nitrate,  and  is  fused  at  the  highest  temperature  of  the 
blast  lamp.  The  fused  mass  is  dissolved  in  water,  acidified,  and  evapo- 
rated to  dryness.  The  residue  is  taken  up  in  hydrochloric  acid,  and  the 
phosphorus  determined  in  the  usual  way,  either  by  weighing  or  by 
titrating  the  yellow  precipitate  with  permanganate." 

14.  Oxygen. — There  is  no  direct  method  for  the  estimation  of 
oxygen  in  coal.     In  an  ultimate  analysis  the  percentages  of 
carbon,  hydrogen,  nitrogen,  sulphur  and  ash  are  added  and  the 
difference  between  this  sum  and  100  per  cent,  is  called  oxygen. 
It  is  thus  apparent  that  any  errors  in  the  estimation  of  the  other 
constituents   are   reflected   in  the   figure   for  oxygen  and  that 
therefore  this  figure  is  to  be  regarded  as  the  least  significant  of 
the  analysis. 

15.  Methods  of  Reporting  Analyses. — The  analysis  is  usually 
made  on  the  air-dried  sample  since  the  sample  in  this  form  is 
least  liable  to  change.     The  original  figures  obtained  by  the 
analyst  will  therefore  be  for  coal  in  this  form.     He  may  now 
take  into  account  the  moisture  lost  in  air-drying  and  calculate 
the  analysis  to  a  basis  of  coal  "as  received,"  he  may  mathemat- 
ically eliminate  all  the  water  and  report  as  "Coal  free  from  Mois- 
ture," or  he  may  by  calculation  eliminate  both  the  moisture  and 
ash  and  report  as  "Coal  free  from  Moisture  and  Ash." 

Numerous  attempts  have  been  made  to  calculate  "true  coal" 
or  "coal  substance"  by  elimination,  in  addition  to  the  moisture 
and  ash,  of  water  of  hydration  contained  in  shale,  and  carbon 
dioxide  contained  in  carbonates  of  the  ash — both  of  which  are 
driven  off  in  whole  or  in  part  with  the  volatile  matter  whereas 
they  really  belong  to  the  ash.  Such  corrections  are  difficult  to 
apply  and  are  not  often  made  in  technical  work.  If  any  event  the 
data  reported  should  be  sufficient  to  allow  a  recalculation  of  the 
results  to  any  other  basis.  Ordinarily  the  air-drying  loss  and 
analysis  of  air-dried  coal  are  reported  since  they  are  the  figures 


212 


GAS  AND  FUEL  ANALYSIS 


actually  obtained  by  the  analyst  and  in  addition  whatever  other 
forms  of  report  may  be  called  for.  The  following  analysis  of  a 
Pittsburg  coal  shows  the  form  of  report. 

PERCENTAGE  COMPOSITION  OF  COAL 


Proximate  analysis 

Air-dried 

As  received 

Calculated 
moisture- 
free 

Calculated 
moisture  and 
ash-free 

Moisture. 

1  07 

3  94 

Volatile  matter  

34.55 

33.55 

34.93 

37.13 

Fixed  carbon  
Ash         

58.51 
5  87 

56.81 
5  70 

59.14 
5  93 

62.87 

100.00 

100.00 

100.00 

100.00 

Ultimate  analysis 
Hydrogen  

5.16 

5.33 

5.09 

5.41 

Carbon  

79  52 

77  21 

80  38 

85.44 

Nitrogen 

1  41 

1  37 

1  43 

1  52 

Oxygen  

6.97 

9.35 

6.09 

6.48 

Sulphur  
Ash 

1.07 
5  87 

1.07 
5  70 

1.08 
5  93 

1.15 

100.00 

100  .  00 

100.00 

100.00 

Air-drvine  loss  .  . 

2.90 

16.  Accuracy  of  Results. — It  will  be  evident  from  a  consider- 
ation of  this  chapter  and  the  preceding  one  on  sampling  that  the 
error  in  sampling  is  liable  to  be  larger  than  the  error  of  analysis. 
The  Joint  Committee  on  Coal  Analysis  in  its  1913  report  esti- 
mates the  allowable  variations  under  its  new  methods  of  analysis 
as  follows: 


Same  analyst, 
per  cent.- 

Different 
analysts, 
per  cent. 

Moisture  under  5  per  cent 

0  2 

0  3 

IVloisture  over  5  per  cent 

0  3 

0  5 

Volatile  matter,  bituminous  coals  
Volatile  matter,  lignites                    

0.5 
1  0 

1.0 
2  0 

Ash  no  carbonates  present 

0  2 

0  3 

Ash  carbonates  present  

0.3 

0.5 

Ash,  more  than  12  per  cent  
Sulphur  in  coal                              .        

0.5 
0.05 

1.0 

0  1 

Sulnhur.  in  coke  .  . 

0.03 

0.05 

THE  CHEMICAL  ANALYSIS  OF  COAL  213 

The  greatest  variation  is  in  the  volatile  matter  and  when  a  con- 
tract is  to  be  awarded  in  which  an  accurate  determination  of 
volatile  matter  is  demanded,  it  is  advisable  for  the  purchaser  and 
the  bidder  to  jointly  analyze  a  single  sample  of  coal  and  harmon- 
ize their  differences  in  analytical  procedure  before  the  contract 
is  awarded.  Lord,1  from  his  wide  experience,  states  that  in 
ultimate  analysis  the  accuracy  can  be  safely  stated  as  within 
0.05  per  cent,  in  the  case  of  hydrogen,  perhaps  0.3  per  cent,  on 
carbon,  0.03  per  cent,  on  nitrogen  and  0.05  per  cent,  on  sulphur. 
17.  Slate  and  Pyrites. — It  is  frequently  desirable  to  determine 
how  much  of  the  pyrites  and  slate  is  in  a  form  which  will  permit 
mechanical  separation  by  coal-washing  or  otherwise.  Lord2 
recommends  the  use  of  calcium  chloride  solutions  with  which  a 
specific  gravity  as  high  as  1.35  may  be  obtained  or  zinc  chloride 
solutions  with  which  a  specific  gravity  of  2.0  may  be  reached. 
The  coal  is  tested  by  crushing  to  various  degrees  of  fineness  and 
determining  the  differences  in  composition  of  the  portion  which 
floats  and  that  which  sinks  in  solutions  of  varying  specific 
gravities. 

1  Jour.  Ind.  and  Eng.  Chem.,  1,  307  (1909). 

2  Jour.  Ind.  and  Eng.  Chem.,  1,  308  (1909). 


CHAPTER  XVI 
HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER 

1.  General  Methods   of  Determining  Heating  Value. — The 
heating  value  of  a  fuel  is  determined  either  directly  in  a  calori- 
meter or  indirectly  by  calculation  from  its  chemical  composition. 
The  direct  calorimetric  method  involves  the  combustion  of  the 
fuel  by  oxygen  supplied  either  as  free  oxygen  gas  or  as  combined 
oxygen  of  some  chemical  compound,  the  operation  being  carried 
out  in  a  closed  vessel  immersed  in  a  known  mass  of  water  under 
conditions  which  ensure  that  the  heat  evolved  in  the  oxidation 
shall  be  with  as  little  loss  as  possible  transferred  to  and  retained 
by  the  calorimetric  vessel  and  the  water.     The  heat  evolved  is 
calculated  from  the  rise  in  temperature  of  the  system. 

Modern  methods  of  calorimetry  really  commenced  with  the 
invention  by  Berthelot  of  his  bomb  calorimeter  described  in  1881. x 
This  has  become  the  standard  method  for  the  determination  of 
heating  values  and  therefore  the  whole  of  this  chapter  is  devoted 
to  it.  Other  methods,  especially  that  of  Parr,  are  described  in 
the  following  chapter. 

2.  The  Bomb  Calorimeter. — Berthelot  showed  that  if  combus- 
tion of  carbon  compounds  took  place  in  a  closed  vessel  in  an  atmos- 
phere of  oxygen  compressed  to  at  leat  seven  atmospheres  and  with 
a  weight  of  combustible  such  that  only  30  to  40  per  cent,  of  the 
oxygen  initially  present  was  consumed,  combustion  was  rapid  and 
complete.     His  bomb  was  lined  with  heavy  platinum  and  was 
very  expensive.     Hempel  in  the  second  edition  of  his  gas  anal- 
ysis published  in  1889  described  a  much  cheaper  bomb  which  had 
no  lining  at  all.     His  modification  has  been  found  by  the  author 
to  be  mechanically  unsatisfactory.     The  neck  of  the  bomb  is 
constricted  so  that  it  is  difficult  to  dry  the  interior,  and  the  head- 
piece is  threaded  and  screws  into  the  neck  roughening  the  lead 

1  Annales  de  Chimie,  5  Serie,  23,  160  (1881).  Annales  de  Chimie,  6  Serie, 
6,  546  (1885). 

214 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER  215 

gasket  as  it  turns  upon  it.  The  method  of  making  connection 
to  the  oxygen  tank  is  also  unsatisfactory. 

Mahler1  in  1892  reported  a  careful  study  of  Berthelot's  method 
as  applied  to  coals,  and  described  a  bomb  of  improved  construc- 
tion with  an  enamel  instead  of  a  platinum  lining.  This  bomb  is 
mechanically  better  than  HempePs,  but  there  is  still  the  objec- 
tion that  the  top  as  it  screws  down,  roughens  the  gasket. 

Atwater2  in  1894  described  a  modification  of  the  bomb  calori- 
meter distinctly  superior  mechanically  to  the  preceding  forms. 
It  resembled  more  closely  the  Berthelot  bomb  than  either  of  the 
others  but,  whereas  the  Berthelot  bomb  was  closed  by  a  tapered 
plug  held  in  place  by  a  screwed  cap,  Atwater's  was  closed  by  a 
flat  cap  held  in  place  by  a  collar  slipped  over  it  and  screwed  over 
threads  on  the  outside  of  the  bomb  after  the  manner  of  a  union 
pipe-fitting.  In  this  way  all  tearing  of  the  gasket  was  avoided. 
The  Atwater  bomb  may  be  provided  with  a  gold  or  platinum 
lining  and  is  to  be  regarded  as  the  highest  type  of  instrument 
for  research  work. 

Many  modifications  of  the  bomb  calorimeter  have  been  made 
by  other  workers,  but  the  principle  has  not  been  changed.  Any- 
one familiar  with  one  instrument  can  readily  learn  to  use  any 
other. 

3.  Details  of  the  Bomb  Calorimeter. — The  bomb  calori- 
meter which  has  been  in  use  in  the  calorimeter  laboratory  of  the 
University  of  Michigan  since  1908  is  shown  in  Figs.  43  and  44. 
It  is  in  general  patterned  after  the  Atwater  bomb,  but  possesses 
several  improvements.  One  of  these,  due  to  Mr.  Edwin  H. 
Cheney,  is  the  octagonal  belt  on  the  body  of  the  bomb  which  fits 
into  a  recessed  plate  and  holds  the  bomb  rigidly  while  the  cover  is 
being  screwed  on.  Another,  due  to  Professor  S.  W.  Parr,  is  the 
deeply  recessed  groove  for  the  gasket  in  the  cover  of  the  bomb 
into  which  the  straight  lip  of  the  bomb  fits  closely  so  that  a 
rubber  gasket  may  safely  be  used.  Improvements  in  various 
details  are  due  to  Mr.  J.  H.  Stevenson,  instrument  maker  of  the 
University  of  Michigan.  Details  of  the  bomb  are  shown  in 
Fig.  43.  It  consists  of  a  cylinder  of  about  300  c.c.  capacity 

1  Bui.  de  la  Societe  d.  Encouragement,  1892,  319. 

2  Starrs  Conn.  Experiment  Station  Report,  1894,  135;  also  J.  Am.  Chem. 
Soc.,  25,  659  (1903). 


216 


GAS  AND  FUEL  ANALYSIS 


machined  from  a  solid  block  of  steel.  On  this  sits  a  cover  carry- 
ing the  oxygen  inlet  and  needle  valve,  also  machined  from  a 
solid  piece  of  steel.  The  cover  is  pressed  tightly  into  place  on 
the  bomb  by  a  heavy  ring  cap  screwing  over  it  and  drawn  up 
tightly  by  a  spanner.  Compressed  oxygen  is  admitted  through 
a  flexible  metal  tube  soldered  at  A  to  the  steel  tube  with  the  coned 
head  B.  This  tube  AB  slides  freely  in  the  threaded  sleeve  C. 
Its  coned  head  makes  a  gas  tight  joint  with  the  bomb  when  C 


C      O 


\\\\\\\^^^^^\\^^^^\\\^\\\\\v 


FIG.  43. — Details  of  calorimetric  bomb. 

is  screwed  up.  The  needle  valve  D  closes  the  bomb  when  it  is 
screwed  down.  The  coal  sits  in  a  flat  nickel  capsule  E  supported 
on  a  brass  ring  which  screws  into  the  head  piece.  The  insulated 
electrical  connection  FG  is  a  brass  rod  coned  where  it  passes 
through  the  head  piece  from  which  it  is  insulated  by  a  bit  of  thin 
rubber  tubing.  The  binding  post  G  screwing  down  on  the 
threaded  end  of  F^  which  projects  through  the  cover  pulls  the 
cone  tightly  into  its  seat  and  makes  a  gas  tight  joint.  A  mica 
disc  placed  between  the-  binding  post  and  the  bomb  completes 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER  217 

the  electrical  insulation  of  the  electrode  from  the  bomb.  The 
gasket  which  fits  into  the  groove  H  may  be  of  lead,  hard 
fiber  or  rubber.  Rubber  gives  a  tight  joint  with  the  least  pres- 
sure of  the  spanner  and  is  therefore  to  be  preferred.  If  it  is  cut 
to  fit  the  groove  accurately  the  inner  lip  of  the  bomb  projecting 
into  the  recessed  head  will  effectually  protect  it  from  the  hot  gases 
evolved  in  the  bomb  during  combustion. 

Fig.  44  shows  the  various  parts  of  the  calorimeter.  Two  bombs 
are  shown,  one  assembled  and  one  taken  apart  and  with  the  head 
sitting  on  a  stand  in  position  for  adjustment  of  the  fine  iron 


FIG.  44. — Bomb  calorimeter. 

firing  wires.     The  nickel-plated  copper  can,  the  stirrer  and  the 
insulating  buckets  are  also  shown. 

The  insulating  buckets  as  shown  in  Fig.  44  consist  of  two  con- 
centric fiber  pails  with  air  in  the  space  between  them.  It  is  in 
many  ways  preferable  to  have  this  space  filled  with  water,  whose 
temperature  may  be  set  at  any  desired  point.  This  minimizes 
the  effect  of  draughts  in  the  room  and  enables  the  operator  to  use 
a  Beckman  thermometer  without  having  to  shift  its  zero  when 
the  room  temperature  fluctuates.  The  temperature  of  the  water 
must  not,  however,  be  so  far  below  room  temperature  that  dew 
will  deposit  on  the  walls  of  the  calorimeter  vessel.  When  a  water 
jacket  is  thus  used  in  the  calorimeter,  it  should  be  provided  with 
a  stirrer  and  its  temperature  should  be  recorded. 


218  GAS  AND  FUEL  ANALYSIS 

4.  Thermometers. — Thermometers  for  the  calorimeters  should 
be  made  especially  for  the  purpose  with  a  stem  below  the  gradua- 
tions long  enough  to  allow  the  bulb  of  the  thermometer  to  be 
opposite  the  center  of  the  bomb.  The  entire  length  of  the  grad- 
uated portion  of  the  thermometer  should  be  visible  above  the 
calorimeter  lid.  It  is  necessary  that  it  be  possible  to  read  the 
rise  in  temperature  to  at  least  0.01°  C.  The  best  thermometers 
are  those  of  the  Beckman  type  with  a  scale  length  of  6°  and  a 
zero  point  adjustable  between  12°  and  25°.  This  type  of  ther- 
mometer is  always  to  be  recommended  where  the  calorimeter 
room  is  of  relatively  constant  temperature  so  that  it  is  not 
necessary  to  change  the  zero  point  often.  Where  this  desirable 
condition  is  not  fulfilled  calorimetric  thermometers  with  a  fixed 
scale  running  from  15°  to  30°  C.  must  be  used.  These  are  usually 
divided  only  into  0.02°  to  avoid  the  excessive  length  of  stem 
which  would  otherwise  result.  The  thermometer  should  in  any 
case  have  been  carefully  calibrated  since  an  error  of  0.01°  on  the 
average  rise  of  3°  means  0.3  per  cent,  or  approximately  40  B.t.u. 
per  pound  of  coal. 

6.  Preparation  of  Sample. — The  methods  to  be  followed  in  ob- 
taining a  representative  sample  from  a  large  quantity  of  coal  and 
the  precautions  necessary  in  grinding,  sampling  and  drying  this 
large  sample  have  been  given  in  Chapters  XIV  and  XV.  It  is 
assumed  here  that  the  sample  is  already  ground  to  a  fineness  of  at 
least  60-mesh  and  has  been  air-dried.  The  amount  of  moisture 
is  immaterial  so  far  as  the  operation  of  the  bomb  calorimeter  is 
concerned,  but  an  air-dried  sample  is  less  likely  to  change  during 
the  operation  of  weighing. 

When  powdered  bituminous  coal  is  burned  in  compressed 
oxygen,  combustion  is  so  violent  that  there  is  danger  that  gas  and 
even  solid  particles  will  be  projected  unburned  through  the  flame 
zone.  The  rate  of  combustion  may  be  materially  lessened  by  re- 
ducing the  surface  of  coal  exposed  to  the  oxygen.  This  is  best 
accomplished  by  briquetting  the  coal.  Most  bituminous  coals 
may  be  readily  compressed  into  pellets  in  a  screw  press.  The 
pressure  should  be  slowly  applied  and  allowed  to  remain  for  a  few 
minutes.  The  resulting  pellet  may  be  trimmed  to  approximate 
weight  with  a  penknife.  It  is  advantageous  to  break  it  into 
two  or  more  pieces  and  discard  the  dust  before  weighing.  The 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    219 

advantage  of  cutting  the  pellet  lies  in  the  readier  ignition,  for 
pellets  which  have  been  pressed  very  hard  are  sometimes  so  dense 
on  the  surface  that  they  fail  to  ignite.  It  is  possible  to  com- 
press some  bituminous  coals  so  firmly  on  the  surface  that  the 
gas  evolved  in  the  interior  of  the  briquette  by  destructive  dis- 
tillation explodes  the  briquette  and  blows  a  cap  of  coke  out  of 
the  crucible.  If  these  dense  briquettes  are  cut  into  several 
pieces,  as  directed  above,  the  trouble  will  be  obviated.  It  is  not 
necessary  to  briquet  anthracite  coals  or  coke.  Indeed,  it  is  not 
possible  to  do  so  without  the  addition  of  a  binder  such  as  sugar 
or  bituminous  coal. 

6.  Manipulation  of  Bomb  Calorimeter. — The  bomb  is  taken 
apart  and  examined  to  see  that  it  is  in  good  condition  and  that 
the  gasket  is  not  cut.  A  few  drops  of  water  are  placed  in  the 
bottom  part  of  the  bomb  which  is  set  in  its  receptacle  in  the 
table-top.  The  top  part  of  the  bomb  is  placed  on  a  ring  of  an  ordin- 
ary ring  stand  as  shown  in  Fig.  44  which  allows  the  heavy  termin- 
als to  drop  through  in  a  convenient  position  for  adj  ustment  of  the 
fuse  wire  and  sample.  The  weighed  sample  of  coal  is  placed  on  a 
shallow  thin  nickel  or  platinum  capsule  resting  on  the  supporting 
ring  suspended  from  the  head  of  the  bomb.  The  capsule  must  be 
almost  flat  to  allow  free  access  of  oxygen  from  the  edges  as  the 
flame  flares  up.  Otherwise  combustion  may  be  incomplete.  It 
must  be  thin  or  it  will  chill  the  flame  and  prevent  complete  com- 
bustion. It  is  advisable  with  anthracite  and  coke  to  place  a  thin 
pad  of  ignited  asbestos  on  the  capsule  in  order  to  decrease  still 
further  the  cooling  effect  of  the  metal. 

A  measured  length,  preferably  not  more  than  two  inches,  of 
the  fine  iron  ignition  wire  34  B.  &  S.  gage  is  attached  to  the 
heavy  wire  terminals  by  winding  the  ends  of  the  fine  wire  several 
times  around  the  heavy  ones,  leaving  the  fine  wire  in  the  form 
of  a  loop  between  the  terminals.  After  making  connections  the 
loop  is  pushed  down  until  it  rests  on  the  fragments  of  coal. 
Care  is  to  be  taken  that  the  wire  does  not  touch  the  metal  capsule 
and  form  a  short  circuit. 

The  cover  with  the  sample  in  position  is  placed  carefully 
on  the  bomb  and  the  threaded  collar  slipped  over  it  and  screwed 
down,  pressure  finally  being  applied  with  the  spanner.  A 
novice  will  nearly  always  screw  the  cover  down  harder  than 


220  GAS  AND  FUEL  ANALYSIS 

necessary,  thus  shortening  the  life  of  the  gasket.  A  moderate 
pressure  will  suffice  if  the  gasket  is  a  good  one.  Gaskets  cut 
from  ordinary  red  fiber  packing  are  too  porous  to  be  tight 
unless  screwed  down  with  great  pressure.  They  may  be  much 
improved  by  vacuum  impregnation  with  a  solution  of  5  grm.  of 
glue  in  5  c.c.  of  glycerine  and  100  c.c.  of  water.  After  impregna- 
tion the  gaskets  are  to  be  dried  in  air  and  rubbed  with  a  piece 
of  paraffine  to  keep  them  from  sticking  to  the  metal. 

The  loose  joint  on  the  end  of  the  flexible  metal  tube  from  the 
oxygen  tank  is  screwed  into  the  head  of  the  bomb,  the  needle 
valve  of  the  bomb  opened  at  least  a  full  turn,  and  then  the 
valve  on  the  oxygen  tank  is  opened  slightly,  the  gas  entering  in  a 
slow  stream  from  the  tank  until  the  gage  shows  20  atmospheres 
pressure.  If  the  valve  on  the  tank  is  opened  relatively  more 
than  the  one  on  the  bomb  the  gage  between  the  two  may  show 
20  atmospheres  before  there  is  that  much  pressure  in  the  bomb. 
The  oxygen  valve  on  the  tank  is  to  be  closed  first  and  after  that 
the  valve  on  the  bomb.  If  the  valve  on  the  bomb  is  closed 
before  that  on  the  tank,  the  pressure  on  the  gage  will  rise  very 
quickly  to  the  full  pressure  of  the  oxygen  tank  which  may  be 
2000  Ib.  and  the  gage  may  be  blown  up. 

The  bomb  is  disconnected  and  placed  in  the  water  of  the 
calorimeter  or  in  a  separate  vessel  of  water  to  test  for  leaks. 
If  bubbles  of  gas  appear  around  the  threaded  ring  the  cover 
must  be  screwed  down  more  tightly,  and  possibly  the  gasket 
may  have  to  be  replaced.  If  bubbles  of  air  come  from  the 
head  it  is  evident  that  the  needle  valve  is  leaking.  It  is  worse 
than  useless  to  try  and  force  it  to  become  tight  by  screwing  down 
the  needle  with  great  pressure.  A  needle  valve  truly  ground 
into  its  seat  is  tight  with  slight  pressure.  If  a  particle  of  grit 
comes  between  the  metal  surfaces  the  application  of  pressure 
causes  it  to  scour  the  polished  surface  and  the  valve  will  leak 
until  it  has  been  again  ground  to  a  true  surface.  In  case  of  a 
leaking  needle  valve  the  pressure  must  be  relieved,  the  bomb 
opened  and  the  needle  valve  unscrewed  entirely  out  of  the 
head.  The  lock  nut  into  which  it  was  threaded  is  also  to  be 
removed.  The  coned  seat  into  which  the  needle  valve  is  ground 
may  now  be  seen  in  a  strong  light.  The  best  policy  is  to  grind 
the  needle  valve  into  its  seat,  an  operation  requiring  not  more 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    221 

than  ten  minutes  if  the  valve  has  not  been  abused.  The  needle 
valve  is  dipped  into  a  paste  of  fine  emery  or  carborundum 
in  water  and  ground  into  its  seat  by  rotating  it  back  and  forth 
with  the  fingers.  A  polished  ring  will  soon  be  visible  on  the 
cone  point  and  a  corresponding  ring  in  the  seat.  When  this 
appears,  unless  the  metal  has  been  badly  scratched,  the  process 
may  be  considered  complete  and  the  grinding  interrupted. 
The  valve  is  to  be  thoroughly  cleaned  from  grit  and  dried,  when 
it  is  ready  for  use. 

The  bomb  when  charged  is  to  be  carefully  centered  in  the 
calorimeter  vessel  which  is  in  turn  centered  in  the  outer  vessels. 
The  stirrer  and  thermometer  are  placed  in  position  and  two 
liters  of  water  whose  temperature  is  approximately  3°  below 
room  temperature  is  added.  A  glass  flask  which  holds  1000 
c.c.  of  water,  contains  the  following  weights  of  water,  when 
balanced  against  brass  weights  in  air.1 

15°  C 998.05grm. 

20°  C 997.18  grm. 

25°  C 996. 04  grm. 

30°  C 994.66  grm. 

The  liter  flasks  of  various  makers  differ  in  the  amount  of 
water  which  they  discharge  and  the  flask  should  be  calibrated 
by  direct  weight  for  some  one  temperature.  It  is  more  con- 
venient for  calculation  purposes  to  calibrate  the  flask  to  deliver 
2000  grm.  of  water  at  the  temperature  most  frequently  used, 
or  sometimes  to  deliver  such  an  amount  of  water  that  the  sum 
of  the  water  added  and  the  water  value  of  the  calorimeter  shall 
be  2500  grm.  It  is  in  many  ways  better  to  weigh  the  water  di- 
rectly into  the  counterpoised  calorimeter  vessel  as  it  sits  on  the 
balance. 

Especial  care  is  to  be  taken  to  see  that  the  thermometer  is 
centered  in  the  space  between  the  bomb  and  the  edge  of  the 
vessel.  If  it  touches  either,  or  even  if  it  is  a  little  off  center 
the  rise  of  the  thermometer  will  not  be  even  and  the  result 
may  be  in  error. 

After  the  adjustments  are  complete  the  stirrer  is  operated 
for  at  least  two  minutes  before  the  first  temperature  reading 

1  Bureau  of  Standards  Bull.  4,  600  (1907-08). 


222  GAS  AND  FUEL  ANALYSIS 

is  made  on  an  even  minute.  Readings  are  to  be  made  each 
minute  thereafter  for  at  least  five  minutes,  the  stirrer  being 
kept  going  steadily  at  30-40  strokes  per  minute  and  the  tempera- 
ture slowly  and  steadily  rising  with  each  reading  as  heat  is 
absorbed  from  the  air  of  the  room,  or  dropping  if  the  calorimeter 
is  above  room  temperature.  This  ends  the  preliminary  period, 
which  must  show  at  least  five  readings  changing  by  regular 
increments  due  solely  to  heat  transfer  to  or  from  the  outside  air. 

The  firing  circuit  is  closed  simultaneously  with  the  last 
reading  of  the  preliminary  period.  The  iron  wire,  becomes 
heated  to  redness,  the  coal  ignites  and  the  iron  wire  fuses  almost 
instantly.  It  is  well  to  have  an  electric  lamp  in  the  firing  circuit 
which  lights  when  the  current  is  turned  on  and  is  extinguished 
when  the  wire  fuses.  An  ammeter  in  the  circuit  answers  the 
same  purpose  showing  that  the  ignition  is  prompt  and  that  an 
undue  amount  of  heat  is  not  imparted  to  the  calorimeter  by  the 
electric  current.  Current  for  ignition  may  best  come  from  a 
storage  battery  or  group  of  dry  cells  giving  about  12  volts. 
Higher  voltages  are  apt  to  cause  insulation  troubles. 

Within  a  half  minute  after  ignition  the  thermometer  begins 
to  rise  so  rapidly  that  it  is  not  possible  to  make  the  thermometer 
readings  accurately.  They  should  be  taken  as  accurately 
as  possible,  and  regularly  on  each  minute.  After  about  three 
minutes  the  thermometer  reaches  its  maximum,  but  the  stirring 
and  temperature  readings  must  be  kept  up  without  intermission 
for  a  total  of  ten  minutes  after  ignition  to  obtain  data  for  the 
radiation  corrections. 

After  the  termination  of  the  thermometer  readings  the  bomb  is 
removed  from  the  calorimeter,  wiped  dry,  and  placed  in  its  recep- 
tacle on  the  table.  The  needle  valve  is  opened  and  after  the 
pressure  is  relieved  the  top  is  removed.  The  coal  should  be 
perfectly  burned  and  the  ash  should  appear  as  fused  beads.  The 
iron  wire  has  burned  as  far  as  the  heavy  conductors  and  in 
accurate  work  the  length  of  the  wire  unburned  should  be  deter- 
mined to  enable  the  proper  correction  to  be  made  for  the  weight  of 
wire  burned.  The  weight  of  wire  burned  comes  to  be  almost 
a  constant  for  each  operator  and  may  be  taken  as  such  in  ordinary 
work.  If  soot  appears  in  the  bomb  or  on  the  capsule,  the  deter- 
mination should  at  once  be  rejected.  With  inexperienced  ope- 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    223 

rators  this  trouble  is  frequently  caused  by  opening  the  valve  on  the 
oxygen  tank  too  fast  when  filling  the  bomb,  with  the  result  that 
the  gage  on  the  connecting  tube  jumps  to  the  proper  reading 
before  the. indicated  pressure  is  reached  in  the  bomb.  If  trouble 
persists  it  may  be  necessary  to  increase  the  oxygen  pressure  to 
25  atmospheres.  The  bomb  is  to  be  rinsed  out  carefully  and 
unless  it  is  to  be  used  again  at  once,  is  to  be  dried  best  in  an  oven 
at  a  temperature  of  about  35-40°  C.  If  the  bomb  is  not  dried  in 
this  way  rust  is  almost  certain  to  form  in  the  needle  valve  and 
prevent  it  from  closing  tightly. 

7.  Thermometer  Corrections. — The  calorimetric  thermometer 
should  have  the  certificate  of  the  Bureau  of  Standards.     In  addi- 
tion to  the  corrections  indicated  on  the  certificate  as  inherent 
in  the  thermometer  on  account  of  variation  in  the  diameter  of  the 
capillary  tube,  etc.,  minor  corrections  must  be  made  in  accurate 
work  for  variations  due  to  the  conditions  under  which  the  ther- 
mometer is  used.     The  Bureau  of  Standards  calibrates  ther- 
mometers when  totally  immersed  in  a  bath  of  the  temperature 
indicated.     In  calorimetric  work  the  bulb  and  part  of  the  stem  is 
within  the  calorimeter,  while  part  of  the  stem  projects  through  the 
cover  of  the  calorimeter  into  the  air  of  the  room.     A  small 
correction  must  be  made  for  this  emergent  stem.     In  the  case 
of  Beckmann  thermometers  an  additional  "  setting  factor  correc- 
tion" must  be  used  in  case  the  thermometer  is  set  for  a  different 
zero  from  that  used  in  the  calibration.     The  formulae  for  these 
corrections  vary  with  different  sorts  of  glass  and  are  given  in 
full  in   the  certificate  of   calibration  accompanying    each  ther- 
mometer.    The  corrections  rarely  amount  to  more  than  a  few 
thousandths  of  a  degree. 

8.  Radiation  Corrections. — The  combustion  of  the  coal  in   a 
bomb  calorimeter  is  probably  a  matter  of  only  a  few  seconds,  but 
it  requires  several  minutes  for  the  heat  to  be  transmitted  to  the 
water  and  for  the  thermometer  to  register  the  rise  in  temperature. 
Adiabatic  calorimeters  have  been  constructed,1  but  they  are  not 
technical  instruments.     With  the  usual  type  of  instrument  radia- 
tion corrections  must  be  made  in  spite  of  careful  jacketing  of  the 
calorimeter.     Their  magnitude  is  lessened  by  adjusting  the  tem- 
perature of  the  water  placed  in  the  calorimeter  with  reference  to 

1  Richards  and  Jesse,  J.  Am.  Chem,  Soc.,  32,  268  (1910). 


224  GAS  AND  FUEL  ANALYSIS 

room  temperature  and  to  the  rise  in  temperature  expected.  If 
the  rise  in  temperature  is  to  be  3°,  the  water  poured  into  the  calori- 
meter should  be  about  3°  below  room  temperature.  When 
equilibrium  is  reached  at  the  time  of  ignition  the  temperature 
will  be  about  2.5°  below  that  of  the  room  and  after  combustion 
it  will  be  about  0.5°  above  room  temperature.  This  arrange- 
ment minimizes  the  errors.  The  temperature  rises  very  rapidly 
after  ignition  to  one  so  nearly  that  of  the  room  that  changes  due 
to  radiation  are  slight  and  repeated  readings  may  be  made  to 
obtain  the  final  temperature.  If  the  final  temperature  of  the 
calorimeter  is  slightly  above  that  of  the  room  there  should  be  a 
maximum  point  in  the  thermometer  readings  with  a  slow  decrease 
thereafter. 

It  is  common  practice  to  consider  that  the  maximum  ther- 
mometer readings  represent  the  actual  maximum  temperature  of 
the  calorimeter,  but  it  is  not  a  safe  assumption,  for  if  the  ther- 
mometer bulb  is  unduly  close  to  the  bomb  or  if  the  stirring  is 
inefficient  the  thermometer  may  rise  too  high  and  fall  rapidly 
again  to  the  temperature  representing  the  true  average  value  of 
the  system,  after  which  it  will  change  slowly  and  regularly  through 
radiation.  It  is,  therefore,  unsafe  to  use  the  maximum  temper- 
ature in  calculations.  The  final  temperature  of  the  combustion 
period  should  be  taken  only  after  sufficient  time  has  elapsed  so 
that  it  is  certain  that  the  system  has  come  to  equilibrium.  Five 
minutes  is  usually  sufficient. 

Radiation  corrections  are  based  on  the  principle  that  the  inter- 
change of  heat  between  the  room  and  the  calorimeter  is  propor- 
tional to  the  difference  in  the  temperature  between  them.  The 
temperature  of  the  room  is  assumed  to  be  a  constant  during  any 
one  operation  and  need  not  even  be  known.  The  formula  for  the 
correction  as  used  by  Regnault  and  developed  by  Pfaundler1  is 
somewhat  complicated  in  appearance,  but  is  simple  in  use. 

Regnault-Pfaundler  Formula. — Three  sets  of  temperature  read- 
ings are  to  be  made.  The  initial  set  must  not  start  until  after  the 
temperature  of  the  calorimeter  has  commenced  to  change 
regularly  due  to  radiation.  It  consists  of  at  least  five  readings 
made  one  minute  apart.  Only  the  first  and  last  readings  and 
the  time  interval  enter  into  the  calculation,  but  it  is  advisable  to 

1  Poggendorfs  Annalen,  129,  115  (1866). 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    225 

record  the  intermediate  readings  as  a  check  on  the  accuracy  of  the 
two  important  ones  and  to  make  sure  that  the  change  of  temper- 
ature is  uniform  as  it  should  be.  At  the  moment  of  taking  the 
final  reading  of  the  initial  period  the  firing  key  is  pressed  and  the 
reading  just  taken  is  recorded,  both  as  the  final  reading  of  the 
initial  period  and  the  first  reading  to  the  combustion  period.  It 
is  to  be  marked  T0. 

During  the  combustion  period  readings  are  to  be  made  and 
recorded  regularly  not  only  till  the  thermometer  reaches  its 
maximum,  but  also  till  it  is  certain  that  the  changes  in  tempera- 
ture are  again  due  solely  to  radiation.  This  period  may  be  five 


A  ot,          cit      ar  A1 

FIG.  45. — Diagram  showing  derivation  of  Regnault-Pfaundler  formula. 

to  ten  minutes.     There  follows  a  final  period  of  five  minutes  to 
fix  the  radiation  losses  for  the  latter  portion  of  the  test. 

The  derivation  of  the  Regnault-Pfaundler  formula  is  as  follows : 

Let  t  =  mean  temp,  of  initial  period, 
t'  =  mean  temp,  of  final  period. 
v  =  loss  per  time  interval  in  initial  period, 
v'  =  loss  per  time  interval  in  final  period. 
To,  Ti,  T2,  Tn  =  temperature  readings  in  combustion  period, 
ti,  t2,  .  .  .  .  tn  =  average  temp,  of  each  interval  during  combus- 

rp      I    rp 

tion  period;  i.e.,  ti  =  — ~ — >  e^c- 

The  special  case  assumed  by  Pfaundler  is  one  where  the  initial 
temperature  is  only  slightly  different  from  room  temperature, 
giving  a  small  value  for  v.  The  final  temperature  is  considerably 
above  room  temperature  and  the  value  of  v'  is  larger  than  v.  The 
geometrical  construction  for  the  Regnault-Pfaundler  formula  is 
shown  in  Fig.  45.  The  demonstration  is  as  follows: 

15 


I 


lip  A.         i  ,  i  lii       " 

Ilr  I 

jrpi              ;  !:'  i  n  "  "•  c  of:..1  r:  j;;i    {' 

III]!  '  i:it>  M  '"  4= vil 


tm^r 

vr-v     _,. 

C  =  the  algebraic  sum  of  all  the  ordina 
n  =  the   number   of   observations   in 
proper. 

V  — v 

.   .  .  tn-nt).' 


•fcorrectiori 


Heat  received  by  the  calorimeter  froi  i  tl  'outside  ni 

sidered  as  negative  and  therefore  in  the  <  >e  ill  case  ass' 

Pfaundler  where  the  initial  temperature  v,  ;i,s  |i|!|:htly  UIK 
temperature  v  was  negative. 

The  correctness  of  the  formula  is  indepe:  lent  of  tit 
values  and  signs  of  v  and  v'. 

The  corrected  rise  in  temperature  of  the  c  1  prioietei* 

R  =  Tn-T0+C 

The  need  of  an  elaborate  correction  f°Ivra4*ilH||| 11; 
less  when  the  calorimeter  is  provided  with  an  adequate  stirrer 
so  that  the  heat  interchange  between  the  bomb  and  the  water  is 
quickly  effected,  and  also  less  when  the  insulating  jacket  is  good 
than  when  it  is  poor.  With  a  well  designed  calorimeter  the 
largest  part  of  the  rise  in  temperature  occurs  in  the  first  minute 
and  if  the  final  temperature  is  only  slightly  above  room  tempera- 
ture radiation  in  succeeding  minutes  is  almost  negligible. 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    227 

SAMPLE  OF  RECORD 

Determination  of  Heating  Value  of  Coal  in  Bomb  Calorimeter. 
Sample  No.  U.  38         Date  Nov.  10, 
Calorimeter  No.  2        Thermometer  No.  4 
Water  Value  of  Calorimeter  475  grin. 

Water  Used  2000  c.c.    =  1995  grm. 

Total  water  equivalent         2470  grm. 

Sample  of  coal  (air-dried)  0.9922  grm. 
Thermometer  readings 

by  minutes  Factors 

19.68.  v    =-0.0025 

19.68'  v'  =+0.0025 

19.69  t    =   19.69 

19.69  t'   =  23.11 

19.69     To 

21.4       Ti 

22.58     T2 

22.95     T3 

23.09  T4 
23.11     T5 

n=5 
23.11 
23  .  1  1  .        Thermometer  corrections 

23.10  Tn   =23.11-0.045=23.065 
23.10  To    =19.69-0.040  =  19.65 


(90.  0+21.  4-5X19.  7)  =  +0.  006°  C. 


R  =23.065-19.65+0.006=3.421°  C. 

3 . 42 1  X  2470  =  8450  calories 

Deduct  for  0.025  grm.  fuse  wire          40 

Deduct  for  1.0  per  cent,  sulphur 

(20  X  .  9922)  =  20        60 

8390  calories 

ooqrj 

Q  g922  =8455  calorie -i  per  gram  of  air-dried  coal 
8455X1.8  =  15,219  B.t.u.  per  pound  of  coal. 

Proximate  Analysis  of  Coal 
Moisture  0.32  por  cent. 

Volatile  Matter         22 . 87  1  cent 

Fixed  Carbon  72.67J 

Ash 


100.00 
Heat  evolved  per  pound  coal  dry  and  free  from  ash  = — =  15936  B.t.u. 


228  GAS  AND  FUEL  ANALYSIS 

The  Dickinson  Formula. — H.  C.  Dickinson  of  the  Bureau  of 
Standards  proposes  a  simpler  formula  whose  derivation  has  not 
yet  been  published.  The  method  of  using  this  formula  as  pub- 
lished in  the  preliminary  report  of  the  Committee  on  Coal 
Analysis  is  given  below. 

"Observe  (1)  the  rate  of  rise  (ri)  of  the  calorimeter  temperature  in 
degrees  per  minute  for  four  or  five  minutes  before  firing,  (2)  the  time 
(a)  at  which  the  last  temperature  reading  is  made  immediately  before 
firing,  (3)  the  time  (b)  when  the  rise  of  temperature  has  reached  six- 
tenths  of  its  total  amount  (this  point  can  generally  be  determined  by 
adding  to  the  temperature  observed  before  firing  sixty  per  cent,  of  the 
expected  temperature  rise,  and  noting  the  time  when  this  point  is 
.reached),  observe  (4)  the  time  (c)  of  a  thermometer  reading  taken  when 
the  temperature  change  has  become  uniform  some  five  minutes  after 
firing,  (5)  the  final  rate  of  cooling  (r2)  in  degrees  per  minute  for  five 
minutes. 

"The  rate  TI  is  to  be  multiplied  by  the  time  b  —  a  in  minutes  and  tenths 
of  a  minute,  and  this  product  added  (subtracted  if  the  temperature  were 
falling  at  the  time  a)  to  the  thermometer  reading  taken  at  time  a.  The 
rate  r2  is  to  be  multiplied  by  the  time  c  —  b  and  this  product  added 
(subtracted  if  the  temperature  were  rising  at  the  time  c  and  later) 
to  the  thermometer  readings  taken  at  the  time  c.  The  difference 
of  the  two  thermometer  readings  thus  corrected,  provided  the  cor- 
rections from  the  certificate  have  already  been  applied,  gives  the 
total  rise  of  temperature  due  to  the  combustion.  This  multiplied 
by  the  water  equivalent  of  the  calorimeter  gives  the  total  amount  of 
heat  liberated.  This  result,  corrected  for  the  heats  of  formation  of 
nitric  and  sulphuric  acids  observed  and  for  the  heat  of  combustion  of 
the  firing  wire  when  that  is  included,  is  to  be  divided  by  the  weight  of 
the  charge  to  find  the  heat  of  combustion  in  -calories  per  gram.  Calories 
per  gram  multiplied  by  1.8  give  the  B.t.u.  per  pound. 
Example: 

OBSERVATIONS 

Water  equivalent  2550  grm. 
Weight  of  charge  1.0535 
Approximate  rise  of  temp.  3.2° 
60  per  cent,  of  approximate  rise  1.9° 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    229 

Time  Temp.  Corrected  temp. 

10-21  15.244°      (Thermometer  corrections  from  the  certificate.) 

22  15.250 

23  15.255 

24  15.261 

25  15.266 

(a)  26        15.272  15.276° 

Charge  fired 

(b)  27-12  17. 2°  1 

(c)  31    18.500°  18.497° 

32  18.498 

33  18.497 

34  18.496 

35  18.494 

36  18.493 

COMPUTATION 

r i  =  0.028°  -4-  5  =  0.0056°  per  minute,     b  -  a  =  1 .2  minutes 

The  corrected  initial  temperature 

is  15.276°+0.0056°X  1.2  =  15.283°. 

r2  =  0.007° -4- 5  =  0.0014°  per  minute;  c-b  =  3.8  minutes 

The  corrected  final  temperature  is  18.497° +0.0014  X 

3.8 =18.502° 

Total  rise  18.502° -15.283° =  3.219° 

Total  calories  2550X3.219 =  8209 

Titration,  etc -_7_ 

Calories  from  1.0535  grm.  coal 8202 

Calories  per  gram 7785 

or  B.t.u.  per  Ib 14013 

In  practice,  the  time  b  — a  will  be  found  so  nearly  constant  for  a 
given  calorimeter  with  the  usual  amounts  of  fuel  that  b  need  be  de- 
termined only  occasionally. 

9.  Corrections  for  Oxidation  of  Nitrogen. — When  coal  is 
burned  on  a  grate  minute  amounts  of  oxides  of  nitrogen  are 
formed  by  the  combination  of  some  of  the  nitrogen  of  the  air  and 
possibly  also  of  the  fuel  with  the  oxygen  of  the  air.  At  the  higher 
temperature  of  combustion  in  the  compressed  oxygen  of  the  cal- 
orimeter more  oxides  of  nitrogen  are  formed  and  account  should 

1  The  initial  temperature  is  15.27°;  60  per  cent,  of  the  expected  rise  is  1.9°. 
The  reading  to  observe  is  then  17.2°. 


230  GAS  AND  FUEL  ANALYSIS 

be  taken  of  the  heat  evolved  in  their  formation.  The  heat  of 
formation  of  aqeous  nitric  acid  from  nitrogen,  oxygen,  and  water 
is  represented,  according  to  Thomsen,  by  the  following  equation. 

2N+50  +  H20  =  2HN03+29800  calories. 

This  corresponds  to  1058  calories  per  gram  of  nitrogen  or  238 
calories  per  gram  of  HNO3.  The  nitric  acid  formed  may  be  esti- 
mated in  bombs  with  platinum  or  gold  linings  by  rinsing  out  the 
bomb  and  titrating  the  washings  with  standard  alkali.  From 
this  total  acidity  is  deducted  the  sulphuric  acid  formed  and  the 
balance  is  considered  nitric  acid.  The  amount  of  nitrogen  oxi- 
dized is  roughly  about  one  per  cent,  of  the  total  nitrogen  present 
whether  introduced  as  free  nitrogen  with  the  oxygen  or  as  com- 
bined nitrogen  of  the  coal.  The  correction  is  not  usually  more 
than  8  calories  and  may  be  considered  to  be  offset  by  the  heat 
absorbed  in  keeping  the  gases  in  the  calorimeter  at  constant 
volume.  (See  §  12.) 

10.  Corrections  due  to  Oxidation  of  Sulphur. — When  sulphur 
or  pyrites  burns  in  the  air  only  about  5  per  cent,  of  the  sulphur 
is  oxidized  to  80s,  the  rest  of  it  remaining  as  SO2.  When  com- 
bustion takes  place  under  high  oxygen  pressure  in  the  bomb  calor- 
imeter a  much  larger  percentage  burns  to  80s  and  correction 
must  be  made  for  it.  The  equations  are: 

S+20  =  S02  gas  +69,100  calories 

S+30+H20  (excess)  =  dilute  H2S04+ 141,100  calories. 

One  gram  of  sulphur  burning  to  SO2  evolves  2165  calories  and 
to  dilute  H2SO4  evolves  4410  calories.  There  should  therefore 
be  a  deduction  made  of  2245  calories  for  each  gram  of  sulphur  thus 
oxidized  in  the  bomb.  The  determination  of  this  oxidized  sulphur 
requires  a  chemical  analysis  of  the  washings  from  the  bomb  which 
adds  greatly  to  the  amount  of  work  required.  The  difficulty  is 
enhanced  by  the  fact  that  sulphur  may  be  present  in  coal  as  free  sul- 
phur, as  sulphur  in  organic  combination,  as  pyrites  or  as  calcium 
sulphate  and  that  the  corrections  will  vary  for  each  of  these  various 
forms.  For  free  sulphur  burning  to  H2S04  the  correction  will  be 
2245  calories  per  gram  as  given  above,  for  sulphur  as  pyrites  2042 l 
calories,  while  for  sulphur  as  gypsum  or  sulphate  of  iron  no  cor- 

1  Somermeier  J.  Am.  Chem.  Sot.,  26,  566  (1904). 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER  231 

rection  is  to  be  made  since  it  is  already  in  the  oxidized  form.  The 
situation  is  further  complicated  by  the  fact  that  free  sulphur  and 
sulphur  in  organic  combination  do  not  burn  completely  to  SO 3  in 
the  bomb  calorimeter  although  apparently  the  sulphur  of  pyrites 
does  burn  completely.  It  is  customary  to  assume  that  all  of  the 
sulphur  in  coal  exists  in  the  form  of  pyrites  and  to  deduct  two 
calories  for  each  milligram  of  sulphur  in  the  sample  of  coal.  This 
procedure  is  not  above  criticism  for  Parr1  has  shown  that  the 
amount  of  sulphate  in  fresh  coal  may  be  as  high  as  one  per  cent, 
and  that  it  doubles  after  six  months  storage  of  the  ground  sam- 
ple in  the  laboratory. 

A  source  of  error  which  should  be  considered  here  is  that  due  to 
the  possible  action  of  the  dilute  sulphuric  acid  formed  upon  the 
inner  surface  of  an  unlined  bomb.  The  bomb  soon  becomes  coated 
with  oxide  on  its  inner  surface  so  the  action  will  be  between  iron 
oxide  and  sulphuric  acid.  According  to  Thomsen  the  reaction 
Fe203XH2O+3H2SO4  (dilute)  evolves  33,840  calories.  This 
means  353  calories  for  each  gram  of  sulphur  involved  or  3.5 
calories  as  the  maximum  error  involved  for  1  grm.  sample  of  a 
coal  containing  1  per  cent,  of  sulphur.  The  error  from  this  source 
is  totally  negligible.  An  expensive  calorimeter  lined  with  gold  or 
platinum  is  unnecessary  except  where  the  greatest  refinements  of 
accuracy  are  sought. 

11.  Correction  Due  to  Combustion  of  Iron  Wire. — The  iron 
fuse  wire  which  burns  to  FeaC^  evolves  1600  calories  per  gram,  or 
1.6  calories  per  mg.  of  iron  burned. 

12.  Reduction   to    Constant    Pressure. — Combustion   in  the 
bomb  calorimeter  takes  place  at  constant  volume  whereas  in 
ordinary    furnace  work   combustion    takes    place    at    constant 
pressure.     Wherever  a  decrease  in  volume  takes  place  on  combus- 
tion as  where  oxygen  unites  with  hydrogen  to  form  water  which 
condenses,  the  gases  in  the  calorimeter  which  should  normally 
have  contracted  after  combustion  have  had  work  done  upon  them 
to  keep  them  at  constant  volume  with  the  disappearance  of  an 
equivalent  amount  of  heat.     The  correction  amounts  to  541  cal- 
ories for  each  gram  molecule  of  gas  which  disappears. 

When  gaseous  oxygen  combines  with  carbon  to  form  CO2  there 
is  no  change  Of  volume  and  hence  no  correction.     The  oxygen  in 
1  Jour.  Ind.  and  Eng.  Chem.  5,  523.  (1913) 


232  GAS  AND  FUEL  ANALYSIS 

the  organic  matter  of  the  coal,  may  for  the  purposes  of  this  cal- 
culation be  considered  to  unite  with  the  hydrogen  of  the  coal  to 
form  water.  No  correction  is  needed  here  since  both  the  hydrogen 
and  the  oxygen  were  in  the  solid  state  before  combustion  and  the 
water  formed  is  a  liquid. 

There  is  always  present  in  coal  an  excess  of  hydrogen  over  that 
sufficient  to  combine  with  the  oxygen  and  this  so-called  available 
hydrogen  burns  with  gaseous  oxygen  to  form  water  which  con- 
denses. The  change  in  volume  is  shown  by  the  equation 

4H(solid)  +  02  =  2H20  (liquid). 

The  gas  which  Disappears  is  oxygen  in  the  proportion  of  one 
molecule  for  each  4  grm.  of  hydrogen.  The  amount  of  available 
hydrogen  in  coals  varies  from  3  to  5  per  cent,  so  that  on  a  gram 
sample  there  would  be  on  an  average  0.04  grm.  of  hydrogen  which 
would  unite  with  0.01  grm.  molecule  of  oxygen  causing  a  correction 
of  5  calories — a  negligible  amount  except  as  it  may  be  considered 
as  balancing  other  minor  errors  such  as  that  due  to  the  oxidation 
of  nitrogen.  With  petroleum  the  correction  will  be  about  three 
times  as  great  as  with  coal. 

13.  Water  Value  of  Calorimeter. — When  combustion  occurs 
in  a  calorimeter  there  follows  a  rise  in  the  temperature  of  both 
the  water  and  of  the  calorimeter  vessel.  It  is  necessary  to  find 
how  many  calories  are  required  to  heat  the  metal  parts  of  the 
calorimeter  one  degree  and  when  this  has  been  accomplished 
the  value  is  translated  for  convenience  of  calculation  into  grams 
of  water  and  called  the  water  value  of  the  calorimeter.  The 
water  value  is  usually  determined  in  three  ways.  The  first  is  by 
calculation  from  the  weight  of  the  metal  parts  and  their  specific 
heats;  the  second  is  by  the  combustion  of  a  pure  substance,  such 
as  sugar,  benzoic  acid  or  naphthalene,  whose  heating  value  is 
known;  and  the  third  is  by  the  addition  to  the  calorimeter  of  a 
definite  amount  of  hot  water  with  the  determination  of  the  rise  in 
temperature  resulting.  The  first  method  is  simple  but  of  only 
approximate  accuracy.  The  second  method  has  the  advantage 
of  tending  to  compensate  for  any  errors  such  as  the  oxidation  of 
nitrogen  in  combustion  and  even  errors  in  the  thermometer  in  so 
far  as  these  are  constant  for  a  series  of  combustions.  The  third 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    233 

method  has  the  advantage  of  being  an  absolute  one,  but  it  will  be 
found  somewhat  more  difficult  of  application. 

First  Method. — The  first  method  requires  simply  that  the 
weights  of  each  of  the  several  different  materials  contained  in  the 
bomb,  the  stirrer,  the  thermometer  and  the  water- containing 
vessel  be  known.  By  multiplying  these  weights  by  the  specific 
heats  as  given  in  the  following  table  the  number  of  calories  is 
obtained  directly. 

TABLE  OF  SPECIFIC  HEATS  l 

Sp.  ht. 

Tool  steel 0. 1087 

Gun  steel %. 0.1114 

German  silver 0 . 094 

Platinum ." 0.032 

Lead 0.030 

Oxygen  (constant  vol.) 0. 157 

Brass 0.094 

Mercury 0 . 033 

Glass 0.19 

The  inaccuracy  of  the  method  lies  partly  in  the  fact  that  it  is 
not  possible  to  determine  the  individual  weights  of  each  of  these 
constituents — e.g.,  the  mercury  in  the  thermometer,  and  partly  in 
the  fact  that  not  all  of  the  materials  thus  weighed  are  heated  in 
actual  practice  to  the  temperature  indicated  by  the  thermometer 
immersed  in  water.  A  large  part  of  the  thermometer  is  outside 
of  the  calorimeter,  a  part  of  the  stirrer  is  constantly  passing  in  and 
out,  and  the  top  of  the  calorimeter  vessel  although  within  the 
calorimeter  is  not  in  contact  with  the  water.  On  the  other  hand 
there  is  some  transfer  of  heat  from  the  calorimeter  vessel  to  its 
j  ackets  of  which  no  account  is  taken .  Fortunately  all  these  errors 
are  minor  ones  but  the  method  can  hardly  be  considered  accurate 
within  3  per  cent. 

Second  Method. — The  method  of  determining  the  water  value  of 
a  calorimeter  by  the  combustion  of  a  substance  of  known  heating 
value  is  the  most  commonly  employed  and  the  most  reliable  one. 
Sugar  and  benzoic  acid  are  substances  which  are  readily  obtained 
in  a  state  of  purity  and  whose  heating  value  has  been  determined 
by  a  number  of  independent  observers.  The  U.  S.  Bureau  of  Stand- 
ards considers  the  following  heating  values  to  be  the  most  reliable : 

1  Atwater  and  Snell,  J.  Am.  Chem.  Soc.,  25,  694. 


234  GAS  AND  FUEL  ANALYSIS 

Cane  sugar 3945  calories  per  gram. 

Benzole  acid 6321   calories  per  gram. 

Camphor 9290  calories  per  gram. 

Naphthalene 9612  calories  per  gram. 

The  values  for  naphthalene  are  not  very  concordant.  The 
heating  values  per  gram  as  given  by  different  authorities  are  as 
follows : 

Berthelot 9692  calories  per  gram. 

Atwater 9628  calories  per  gram. 

Fischer  &  Wrede 9668  calories  per  gram. 

The  recent  work  of  Richards  and  Jesse1  has  shown  that  very 
special  precautions  are  necessary  for  the  complete  combustion  of 
volatile  hydrocarbons,  and  it  is  probable  that  incomplete  combus- 
tion is  in  part  to  blame  for  the  disagreement  in  the  values  for 
naphthalene. 

The  procedure  in  determining  the  water  value  is  exactly  the 
same  as  for  the  combustion  of  a  fuel.  A  sufficient  amount  of  the 
pure  material  is  pressed  into  a  pellet  so  that  the  heat  evolved  by  its 
combustion  will  be  7000-8000  calories.  This  is  placed  in  the 
bomb  which  is  charged  with  oxygen,  set  in  the  calorimeter  and 
fired,  the  temperature  readings  being  made  as  usual.  In  the 
final  calculations  the  unknown  to  be  solved  for  is  the  mass  of 
water  equivalent  to  the  calorimeter  which  has  been  heated.  The 
difference  between  this  value  and  the  mass  of  water  actually 
added  gives  the  water  value  of  the  calorimeter. 

The  method  of  conducting  the  combustion  is  the  same  as  that 
for  coal  and  should  be  recorded  according  to  the  form,  §  8.  The 
following  example  gives  the  method  of  calculation. 

Total  heat  evolved 

from  benzole  acid 1 . 0856  X  6320  =6860  calories 

from  iron  wire. .  .  .0.022    Xl600=     35 


6895 

Corrected  rise  in  temperature  2.854°  C. 
Heat  absorbed  by  water  2000  X2 . 854  =  5708 


Heat  absorbed  by  calorimeter  1187  calories 

1 1 87 
Water  value  =  S-Q  *7  =  415 

Z.oO4 

1  J.  Am.  Chem.  Soc.,  32,  268  (1910). 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    235 

The  accuracy  of  this  process  is  dependent  first  on  the  purity 
of  the  materials  used  as  a  standard.  Samples  of  pure  substances 
with  certified  heat  value  should  be  obtained  from  the  Bureau 
of  Standards.  The  accuracy  is  also  affected  by  errors  in  the  ther- 
mometer, errors  due  to  oxidation  of  nitrogen,  etc.,  but  in  this 
very  fact  lies  one  of  the  valuable  points  of  the  method.  For. if 
it  be  assumed  that  with  a  thermometer  set  at  a  given  zero  there 
is  an  error  of  0.02°  in  a  rise  of  three  degrees  and  that  there  is  a 
correction  of  8  calories  to  be  made  with  oxygen  from  a  certain 
tank  when  a  sample  of  sugar  which  gives  a  rise  of  3°,  is  burned, 
and  both  of  these  corrections  be  neglected,  it  is  evident  that  the 
water  value  obtained  will  be  in  error.  But  if  this  erroneous  water 
value  be  used  in  the  calculations  of  the  heating  value  of  a  coal 
where  the  errors  due  to  the  thermometer  and  the  oxidation  of 
nitrogen  are  the  same  as  in  the  combustion  of  sugar,  and  where  the 
total  rise  in  temperature  is  approximately  the  same,  the  erroneous 
water  value  will  compensate  for  the  errors  on  the  coal  test  and  the 
result  of  the  coal  test  will  be  correct. 

Third  Method. — The  third  method  of  determining  the  water 
value  of  a  calorimeter  requires  that  the  instrument,  set  up  as 
if  for  a  combustion  except  that  there  is  no  water  in  the  calor- 
imeter vessel,  be  allowed  to  stand  in  a  room  free  from  draughts 
and  of  quite  constant  temperature  until  all  parts  of  the  instru- 
ment have  come  to  a  uniform  temperature  which  is  correctly 
indicated  by  the  thermometer.  This  requires  several  hours. 
The  same  mass  of  water  as  used  in  a  regular  determination  is 
brought  to  a  temperature  approximately  three  degrees  above 
or  below  that  of  the  calorimeter  and  its  temperature  is  accurately 
observed.  This  can  best  be  done  with  the  help  of  the  thermom- 
eter taken  from  the  calorimeter.  If  the  calorimeter  is  at  room 
temperature  there  is  no  danger  of  its  changing  within  the  few 
minutes  necessary  for  the  next  steps.  There  is  a  decided  danger 
of  change  of  temperature  of  the  water  to  be  added,  and  to  guard 
against  error  it  should  be  kept  in  a  flask  as  carefully  insulated 
as  possible  and  stirred  so  as  to  be  of  uniform  temperature  through- 
out. A  vacuum  flask  or  thermos  bottle  with  a  wide  mouth  is 
excellent.  The  temperature  of  the  calorimeter  and  that  of  the 
water  having  been  noted  the  lid  of  the  calorimeter  is  removed, 
the  water  quickly  poured  in  and  the  mixture  stirred,  while  the 


236  GAS  AND  FUEL  ANALYSIS 

usual  temperature  observations  are  made.  Part  of  the  heat 
given  off  by  the  water  has  been  used  to  warm  the  calorimeter 
and  part  has  been  lost  in  radiation.  The  amount  of  heat  re- 
ceived by  the  calorimeter  divided  by  the  rise  in  temperature 
gives  the  water  value.  This  method  gives  values  which  are 
entirely  independent  of  any  errors  due  to  impurity  in  sugar 
or  benzoic  acid  or  to  oxidation  of  nitrogen,  etc.  If  carefully 
carried  out  it  is  a  satisfactory  method. 

This  method  in  its  most  accurate  form  imparts  a  definite 
amount  of  heat  to  the  calorimeter  electrically,  instead  of  by 
added  hot  water.  A  fine  wire  coil  of  known  resistance  is  placed 
in  the  calorimeter  and  an  electric  current  of  carefully  measured 
voltage  and  amperage  passed  through  it  for  a  definite  time.  The 
method  is  used  in  research  laboratories,  but  is  hardly  to  be  con- 
sidered a  technical  method,  and  is  not  described  here  in  detail. 

14.  Accuracy  of  Results. — It  is  the  aim  to  determine  by  com- 
bustion in  the  bomb  calorimeter  the  amount  of  heat  which 
would  be  evolved  by  the  combustion  of  a  fuel  in  the  outside  air. 
This  standard  is  not  an  absolute  one,  for  not  only  will  carbon 
be  burned  to  carbon  dioxide  and  hydrogen  to  water  in  an  ordi- 
nary fire  but  also  sulphur  will  be  burned,  in  part  to  862  and  in 
part  to  SOs,  and  small  amounts  of  nit**c';en  will  be  burned.  In 
applying  corrections  to  the  figures  obtained  in  the  bomb  calor- 
imeter it  is  customary  to  assume  that  all  of  the  sulphur  of  the 
coal  burns  to  80s  in  the  bomb,  and  that  all  of  it  burns  to  SOz 
in  the  air,  and  that  no  nitrogen  is  oxidized  on  combustion  of 
coal  in  air.  The  errors  introduced  by  these  assumptions  are 
small  and  are  usually  neglected.  The  accuracy  of  the  estimation 
of  the  amount  of  heat  evolved  by  combustion  in  the  bomb  will 
depend  on  the  accuracy  with  which  the  water  value  of  the  system 
is  known,  the  care  taken  in  making  radiation  corrections  and  the 
accuracy  with  which  the  rise  in  temperature  is  measured.  This 
last  usually  involves  the  largest  error.  If  the  error  is  0.01°, 
it  will  amount  to  about  0 . 3  per  cent,  or  50  British  thermal  units. 
When  care  is  taken  in  every  detail  and  apparatus  of  superior 
quality  is  used  the  agreement  between  duplicate  determinations 
will  be  closer  than  this  but  it  is  certainly  not  safe  to  claim  a 
closer  absolute  accuracy  since  according  to  Jesse1  the  highest 

1  Jour.  Ind.  and  Eng.  Chem.,  4,  748  (1912). 


HEATING  VALUE  OF  COAL  BY  THE  BOMB  CALORIMETER    237 

authorities  differ  by  0.25  per  cent,  as  to  the  absolute  heating 
value  of  sugar  and  benzoic  acid.  The  Committee  on  Coal 
Analysis  states  that  in  their  judgment  results  obtained  by  a 
single  analyst  should  not  differ  more  than  0 . 3  per  cent,  and  that 
results  obtained  by  different  analysts  should  not  vary  by  over 
0.4  per  cent.  This  high  standard  can  only  be  attained  when 
every  precaution  is  observed. 

15.  Gross  and  Net  Heating  Values. — The  heating  value  of 
the  fuel  computed  by  the  method  given  above  gives  the  total 
heat  developed  when  the  water  formed  condenses  to  a  liquid 
within  the  calorimeter.  This  gives  the  total  amount  of  heat  or 
the  " gross"  heat  value.  In  most  industrial  opperations  the 
water  escapes  as  steam,  and  if  deduction  is  made  for  its  latent 
heat,  a  lower  "net"  heating  value  is  obtained.  This  "net" 
figure  gives  a  closer  approximation  to  the  heat  which  is  ordi- 
narily utilized,  but  it  does  not  give  it  accurately,  because  an 
arbitrary  assumption  has  been  made  as  to  the  temperature 
of  the  escaping  gases.  It  is  customary  to  report  the  total 
heating  value  of  the  coal  and  allow  the  consumer  to  put  such 
a  factor  on  it  as  will  indicate  its  relative  efficiency  for  the 
purpose  to  which  he  intends  to  put  it.  The  method  of  calcula- 
tion of  net  heating  values  is  given  in  §  12  of  Chapter  VII  on 
Heating  Value  of  Gas. 


CHAPTER  XVII 

HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER 
AND  OTHER  METHODS 

1.  Introduction. — The  preceding  chapter  was  devoted  to  a 
discussion  of  the  bomb  calorimeter  as  .the  standard  instrument 
for  the  determination  of  the  heating  value  of  coal.     The  present 
chapter  will  deal  with  other  methods,  such  as  combustion  in 
stream  of  oxygen,  combustion  with  chemicals  like  sodium  per- 
oxide, and  calculation  of  the  heating  value  from  the  chemical 
composition  of  the  coal. 

2.  Combustion  in  a  Stream  of  Oxygen. — Calorimeters  of  this 
type  have  become  obsolete  on  account  of  difficulties  of  manipu- 
lation and  sources  of  error.     The  temperature  of  the  oxygen 
flowing  in  must  be  accurately  measured  and  also  the  temperature 
of  the  gases  flowing  out,  for  correction  must  be  made  for  the  heat 
which  these  streams  of  gas  carry.     The  great  source  of  error  is 
the  incomplete  combustion  of  the  coal.     With  bituminous  coals 
the  smoke  may  frequently  be  seen  issuing  from  the  instrument 
and  even  with  anthracite  and  coke,  carbon  monoxide  may  always 
be  found  in  the  escaping  gases.     Accurate  results  have  been 
obtained  with  this  type  of  calorimeter  but  only  after  laborious 
correction  for  the  large  number  of  errors. 

3.  The  Thompson  Calorimeter. — A  very  crude  form  of  calor- 
imeter which  has  also  become  obsolete  was  that  of  Lewis  Thomp- 
son.    He  mixed  powdered  coal  with  potassium  chlorate  and 
nitrate,  placed  the  mixture  in  a  calorimeter  vessel  and  fired  the 
charge.     The  method   and  apparatus  were   crude  throughout 
but  the  greatest  source  of  error  lay  in  the  heat  absorbed  in  the 
decomposition  of  the  chlorate  and  nitrate.     When  coal  burns 
under  a  boiler  it  unites  with  gaseous  oxygen  to  form  CC>2  and  H20. 
Essentially  the  same  result  takes  place  in  a  bomb  calorimeter. 
When,  however,  the  oxygen  is  taken  from  one  form  of  chemical 
combination  and  is  made  to  combine  with  the  coal  to  form  a 
different  compound,  the  result  is  not  at  all  the  same  as  that 

238 


HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER    239 


obtained  in  the  combustion  of  the  coal  with  gaseous  oxygen  and 

the  corrections  to  be  applied  must  be  worked  out  with  great  care. 

Scheurer-Kestner1  determined  that  if  15  per 

cent,  was  addec}  to  the  heating  value  obtained 

with  the  Thompson"  calorimeter, '  the  results 

never  differed  by  more  than  4  per  cent,  from 

those  obtained  by  the  Favre  and  Silverman 

calorimeter  which  burns  the  coal  in  a  stream 

of  oxygen. 


FIG.  46. — Parr  calorimeter. 


D' 


FIG.  47.— Details  of 
Parr  calorimeter. 


4.  The  Parr  Calorimeter. — Parr2  proposed  sodium  peroxide  as 
a  chemical  to  be  used  in  oxidizing  coal  in  a  calorimeter,  worked 
out  the  corrections  to  be  applied,  and  devised  a  very  practical 

1  Bull.  Soc.  Ind.,  Mulhouse,  506,  1888. 

2  Jour.  Am.  Chem.  Soc.,  22,  646  (1900). 
Jour.  Am.  Chem.  Soc.,  24,  167  (1902). 
Jour.  Am.  Chem.  Soc.,  29,  1606  (1907). 
The  Chemical  Engineer,  6,  253  (1907). 
/.  Ind.  and  Eng.  Chem.,  1,  673  (1909). 


240  GAS  AND  FUEL  ANALYSIS 

calorimeter.     He  writes  the  probable  reactions  in  the  calorimeter 
as  follows  : 

2Na202+C  =  Na2CO3+Na2O 


There  is  more  heat  evolved  in  each  of  these  reactions  than  in  the 
combustion  of  carbon  and  hydrogen  with  gaseous  oxygen  but 
fortunately  the  reduction  factor  is  closely  the  same  for  both  of 
them.  The  heat  evolved  by  the  combustion  of  carbon  and  hydro- 
gen in  the  Parr  calorimeter  multiplied  by  0.73  gives  the  true  heat 
value.  Smaller  corrections  are  to  be  made  for  the  dissociation 
of  the  KClOs  used,  for  the  oxidation  of  sulphur,  the  combustion 
of  the  fuse  wire,  the  fusion  of  the  ash,  and  the  hydroxyl  or 
combined  water  present  in  coal. 

Since  the  oxygen  is  introduced  as  a  solid  and  the  Na2COs  and 
NaOH  formed  in  the  reaction  are  also  solids,  the  bomb  need  not 
be  made  to  resist  high  gas  pressures  but  may  be  made  of  thin 
metal. 

The  general  arrangement  of  the  calorimeter  is  shown  in  Fig. 
46  where  B  and  C  are  two  fiber  buckets  acting  as  heat  insulators, 
A  is  the  can  for  water,  and  D  the  combustion  bomb  which  sits 
upon  a  cone  F  and  is  rotated  by  a  belt  running  in  the  pulley  P. 
The  stirring  is  very  effectively  accomplished  by  the  removable 
wings  shown  attached  to  the  bomb  which  force  the  water  down 
the  annular  space  between  the  bomb  and  the  shell  E  out  of  open- 
ings at  the  bottom  and  up  again  on  the  outside. 

Details  of  the  bomb  are  shown  in  Fig.  47  where  A  is  the  brass 
shell  closed  at  each  end  by  a  plate  and  gasket  held  in  place  by  a 
screwed  cap.  The  top  plate  forms  the  bottom  of  the  stem  B 
which  carries  in  its  center  the  insulated  wire  KJI  of  the  firing 
circuit.  The  lower  cap  D  together  with  the  sleeve  E  forms  an 
air  chamber  around  the  lower  portion  of  the  bomb  which  prevents 
too  sudden  cooling  of  the  fused  mass  and  thus  allows  time  for 
completion  of  the  reaction. 

5.  Preparation  of  Parr  Calorimeter.  —  The  bomb  must  be 
thoroughly  dry  and  the  gaskets  in  good  condition.  It  is  best  to 
dry  the  parts  after  each  test  in  an  oven  and  to  examine  them 
carefully  before  putting  them  together.  The  lower  cap  C  is 
fitted  into  place,  the  outer  sleeve  E  screwed  on  and  the  plug 


HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER    241 

D  screwed  firmly  down  with  the  wrench  provided.  Water 
leaking  into  the  bomb  always  spoils  the  determination  and  may 
cause  an  explosion. 

The  coal  is  to  be  ground  to  pass  a  100-mesh  sieve  in  order  that 
it  may  react  rapidly  with  the  peroxide.  Anthracite  coal,  coke, 
semi-bituminous  and  eastern  bituminous  coals  in  which  the 
moisture  will  not  exceed  3  per  cent,  may  be  used  in  an  air-dry 
condition.  Other  bituminous  coals,  lignites,  peats,  etc.,  must  be 
dried  at  105°  C.  before  use  to  avoid  the  reaction  between  the 
hygroscopic  moisture  and  the  peroxide  with  evolution  of  heat  in 
the  calorimeter.  The  danger  of  change  in  the  coal  sample  during 
the  processes  of  drying  and  grinding  is  treated  in  Chapter  XV  on 
Chemical  Analysis. 

It  is  necessary  to  secure  very  intimate  mixture  of  the  coal,  the 
Na2C>2  and  the  KClOs  added  as  an  accelerator  of  combustion. 
Professor  Parr  recommends  that  1  grm.  of  the  dry  and  finely 
ground  KClOs  be  weighed  into  the  bomb  first,  and  to  that  be 
added  0.5  grm.  of  the  coal  prepared  as  directed  above  and  that 
the  two  be  mixed  by  stirring  with  a  glass  rod.  To  this  is  added 
approximately  10  grm.  of  sodium  peroxide  which  may  be  meas- 
uerd  with  sufficient  accuracy  in  the  scoop  provided  with  the 
instrument.  The  contents  of  the  bomb  are  next  to  be  thoroughly 
mixed  by  shaking.  If  this  were  done  after  the  regular  top  and 
firing  wire  were  in  place  the  firing  wire  would  almost  certainly 
become  twisted  and  short  circuited,  so  it  is  better  to  use  the  false 
top  provided.  It  is  well  at  the  beginning  of  the  shaking  process 
to  invert  the  cartridge  and  tap  it  sharply  on  the  desk  to  dislodge 
any  coal  which  may  have  stuck  to  the  bottom.  When  the  mixing 
is  complete  the  bottom  of  the  cartridge  may  be  tapped  lightly 
against  the  desk  to  dislodge  any  material  sticking  to  the  cap. 
The  regular  top  to  which  about  4  in.  of  fine  iron  wire  (32  or 
34  American  gage)  has  been  attached  in  a  loop  as  shown  at  G 
of  Fig.  47  is  now  placed  carefully  in  position  and  screwed  into 
place.  Care  should  be  taken  after  this  has  been  adjusted,  not  to 
tip  the  bomb  since  the  fine  iron  wires  are  easily  crossed.  The 
spring  stirring  clips  may  now  be  adjusted  and  the  apparatus  set 
up  as  shown  in  Fig.  46. 

The  strength  of  the  firing  current  will  vary  between  2  and  4 
amperes.  It  should  be  adjusted  by  trials  in  the  open  air  until 

16 


242  GAS  AND  FUEL  ANALYSIS 

the  wire  fuses  promptly  on  closing  the  switch.  Where  electric 
current  for  ignition  is  not  available  another  form  of  calorimeter 
head  may  be  used  which  allows  ignition  by  a  hot  wire  slug  dropped 
through  the  hollow  stem.  The  specified  dimensions  of  the  slug 
for  this  purpose  are  1  cm.  long,  and  2.5  mm.  diameter.  This 
gives  a  weight  of  a  little  over  0.3  grm.  and  involves  a  correction 
of  about  .022°  F. 

6.  Care  of  Sodium  Peroxide. — Sodium  peroxide  is  hygroscopic 
and  absorbs  moisture  from  the  air.  even  when  preserved  in  appar- 
ently well-stoppered  bottles,  forming  Na2O2.2H20.     The  effect 
of  this  hydrate  formation  is  illustrated  by  an  experiment  made  by 
Professor  Parr.     He  exposed  10  grm.  of  sodium  peroxide  on  a 
watch  glass  in  the  laboratory  for  an  hour  and  found  that  it  had 
gained  in  weight  nearly  0.5  grm.     This  peroxide  when  used  in 
the  calorimeter  gave  a  rise  in  temperature  higher  by  0.194°  than 
the  pure  peroxide.     As  the  total  correct  rise  of  temperature  in 
this" experiment  was  only  2.180°  it  will  be  seen  that  the  error  was 
almost  9  per  cent. 

The  sodium  peroxide  should  not  only  be  pure  and  anhydrous 
but  should  also  be  in  grains  of  the  proper  size.  If  the  peroxide 
is  too  coarse  the  powdered  coal  tends  to  sift  to  the  bottom  of  the 
bomb  and  escape  combustion.  If  peroxide  is  too  fine  the  reac- 
tion is  sometimes  very  violent.  The  manufacturers  of  the  calor- 
imeter furnish  reliable  peroxide  in  small  hermetically  sealed  cans 
and  also  furnish  a  clamp-top  fruit  jar  which  is  said  to  preserve  the 
contents  of  a  single  can  during  its  use. 

Sodium  peroxide  reacts  at  ordinary  temperatures  with  all 
organic  substances  in  presence  of  moisture  with  evolution  of  heat 
often  sufficient  to  produce  flame  or  explosion.  Mixtures  of 
sodium  peroxide  and  coal  which  may  have  to  be  disposed  of  are 
not  to  be  thrown  into  waste  jars.  They  may  be  cautiously  and 
slowly  poured  into  a  vessel  containing  considerable  water  which 
will  absorb  the  heat  and  prevent  violent  reactions.  Sodium 
peroxide  causes  bad  burns  on  the  skin. 

7.  Operation  of  Parr  Calorimeter. — The  bomb  prepared  as 
above  directed  is  placed  in  the  calorimeter  vessel  and  properly 
centered.     Two  thousand  grams  of  water  are  then  added  to  the 
calorimeter  vessel.     It  is  preferable  that  the  temperature  of  the 
water  should  be  about  2.0°  C.  below  room  temperature  for  the 


HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER    243 

radiation  correction  will  be  less  under  these  conditions.  The 
thermometer  is  adjusted  and  the  bomb  started  to  rotating  at  the 
rate  of  about  100  revolutions  a  minute.  Temperatures  are  to 
be  read  at  the  end  of  each  minute.  Within  two  or  three  minutes 
the  readings  of  the  thermometer  should  become  almost  constant 
except  for  the  regular  and  very  slight  change  due  to  radiation. 
Should  the  thermometer  rise  irregularly  and  more  rapidly  than 
0.01  or  0.02°  per  minute  during  this  preliminary  period,  there  is 
probably  a  slight  leak  of  water  into  the  bomb.  The  operation 
must  be  at  once  stopped,  the  bomb  taken  out,  wiped  dry  on  the 
outside,  opened  and  emptied.  A  leaky  bomb  is  not  .only  inac- 
curate but  dangerous.  After  five  readings  at  intervals  of  one 
minute  each  in  the  preliminary  period  have  shown  only  this 
slight  and  regular  change  of  temperature,  ignition  is  effected  by 
closing  the  switch  on  the  cover  of  the  instrument.  The  thermome- 
ter rises  very  rapidly  owing  to  the  thin  walls  of  the  bomb  and 
the  efficient  stirring  and  usually  reaches  its  maximum  after  two 
minutes.  Nevertheless  observations  should  be  continued  for  at 
least  eight  minutes  after  ignition  to  allow  corrections  for  radia- 
tion to  be  made. 

The  bomb  is  then  removed  from  the  water,  wiped  dry  and 
opened.  There  should  be  no  trace  of  unburned  carbon  visible, 
nor  any  odor.  The  lower  plug  is  removed  and  the  fused  cake  in 
the  bottom  of  the  bomb  knocked  into  a  casserole  containing 
about  500  c.c.  of  water.  The  bomb  should  also  be  placed  in  the 
water  until  all  the  fused  peroxide  has  dissolved.  It  is  then 
removed,  rinsed  out  and  dried. 

The  solution  in  the  casserole  is  to*be  tested  for  unburned  car- 
bon. As  an  alkaline  solution  it  contains  black  flakes  of  oxides  of 
iron  and  copper.  After  acidification  it  becomes  a  clear  yellow 
solution,  with  carbon  as  the  only  matter  in  suspension,  the  silicic 
acid  remaining  in  solution  in  the  large  volume  of  water.  If  any 
unburned  carbon  is  visible  it  should  be  filtered  on  a  Monroe  or 
Gooch  crucible,  dried  and  weighed.  A  correction  of  8.1  calories 
must  be  made  for  each  milligram  of  unburned  carbon.  This 
precaution  should  never  be  omitted  by  a  beginner  nor  where 
accurate  work  is  important. 

The  corrected  rise  of  temperature  may  be  calculated  according 
to  the  formulas  given  in  Chapter  XVI,  but  a  simpler  method  will 


244  GAS  AND  FUEL  ANALYSIS 

usually  suffice  since  this  calorimeter  is  not  used  where  the  greatest 
accuracy  is  required.  It  is  sufficiently  accurate  to  assume  that 
the  average  change  in  temperature  per  minute  during  the  final 
period  represents  also  the  change  due  to  radiation  for  each  minute 
during  the  combustion  period.  The  errors  involved  in  this 
assumption  are  small  since  the  temperature  in  the  combustion 
period  rises  to  almost  its  full  value  in  the  first  minute.  The  tem- 
perature at  the  end  of  the  fourth  minute  after  ignition,  may  be 
taken  as  the  end  of  the  combustion  period  and  corrections  as 
shown  by  the  next  four  minutes'  readings,  applied  to  it.  Cor- 
rections for  potassium  chlorate,  sulphur,  ash,  etc.,  as  given  in 
the  following  section  are  to  be  deducted  from  this  reading, 
the  result  being  the  corrected  final  temperature. 

The  instrument  as  furnished  by  the  makers  has  a  standard 
water  equivalent  of  135  grm.  The  corrected  rise  in  tempera- 
ture multiplied  by  2135  and  by  the  factor  .73  and  divided  by  the 
weight  of  the  sample  in  grams  gives  the  heat  value  in  calories 
per  gram.  The  figure  may  be  converted  into  British  thermal 
units  per  pound  by  multiplying  it  by  1.8. 

8.  Corrections  to  be  Applied  with  Parr  Calorimeter. — Parr  has 
worked  out  very  carefully  the  correction  to  be  applied  and  pub- 
lished his  results  in  the  journals  cited  as  references  at  the  com- 
mencement of  this  chapter.  He  has  shown  that  the  ratio  of  the 
heat  evolved  in  the  combustion  of  carbon  and  hydrogen  with 
gaseous  oxygen  to  that  evolved  on  combustion  with  sodium 
peroxide  is  very  closely  represented  by  the  factor  0.73.  The 
KClOs  used  as  an  accelerator  evolves  an  additional  amount  of 
heat.  Similar  corrections  are  required  for  ash,  sulphur,  fuse 
wire,  and  hydroxyl  constituents  of  the  coal.  Since  the  calor- 
imeter is  always  furnished  with  a  standard  water  value  these 
corrections  may  be  calculated  in  terms  of  temperature.  Profes- 
sor Parr's  latest  corrections1  are  as  follows,  the  charge  being 
0.5  grm.  coal,  10  grm.  Na2O2  and  1  grm.  KCKV  The  corrections 
are  to  be  subtracted  from  the  observed  rise  in  temperature. 

Each  per  cent,  ash  is  multiplied  by 0.00275°  C. 

Each  per  cent,  sulphur  is  multiplied  by 0.005°  C. 

Correction  for  heat  reaction  of  KClO3(l.g.) is 0. 130°  C. 

Heat  of  combustion  of  fuse  wire  (10  mg.)  is 0.008°  C, 

1  J.  Ind.  and  Eng.  Ghent.,  1,  673  (1909) 


HEATING  VALUE  OF  COAL  BY  THE  PARR  CALORIMETER    245 

Heat  brought  in  by  hot  ignition  slug  is 0.012 

Correction  for  water  of  composition  in  bituminous 

coals  with  over  30  per  cent,  volatile  matter  is 0.025°  C. 

Correction  factors  for  hydroxyl  in  other  substances  are  as  follows, 
when  0.5  grm.  material  is  taken  for  combustion. 

Brown  lignites 0 . 050°  C. 

Wood 0.111 

Sugar 0.145 

Benzoic  acid 0 . 124 

The  water  value  of  the  calorimeter  may  be  experimentally 
determined  by  direct  weight  of  the  various  parts  or  by  combustion 
of  a  pure  substance  as  described  in  Chapter  XVI.  The  latter 
method  is  not  so  satisfactory  as  it  is  with  the  bomb  calorimeter, 
since  it  involves  the  use  of  the  factor  0.73.  Benzoic  acid  and 
sugar  involve  also  the  added  correction  for  hydroxyl. 

It  is  difficult  to  get  ignition  of  anthracite  and  coke  without 
adding  a  small  amount  of  some  readily  combustible  substance 
such  as  benzoic  acid.  The  heating  value  of  benzoic  acid  is  6320 
calories  per  gram  and  in  the  Parr  calorimeter  0.2  grm. will  evolve 

jp^g  calories  plus  the  added  calories  due  to  its  hydroxyl  contents. 

Reducing  this  to  a  temperature  basis  it  amounts  to  0.811+0.050° 
C.  =0.861°  C.  to  be  subtracted  in  case  0.2  grm.  benzoic  acid  is 
used  as  an  igniter. 

9.  Accuracy  of  Parr  Calorimeter. — The  work  of  Professor  Parr 
has  shown  definitely  that  accurate  results  may  be  obtained  with 
this  calorimeter,  but  it  has  also  shown  that  this  accuracy  can  be 
gained  only  by  the  observation  of  precautions  and  the  use  of 
corrections  which  deprive  the  process  of  much  of  the  simplicity 
which  formerly  characterized  it.     Accurate  results  are  dependent 
on  the  quality  of  the  peroxide  used,  a  point  which  must  usually 
be  taken  on  faith.     The  calculations  involve  a  knowledge  of  the 
ash,  sulphur,  and  volatile  matter  of  the  coal,  and  the  application 
of  corrections  for  these  constituents.     These  points  prevent  the 
method  from  being  a  standard  one  as  is  combustion  in  the  bomb 
calorimeter,  but  do  not  prevent  it  from  being  a  useful  commercial 
instrument  where  the  highest  accuracy  is  not  required. 

10.  Calculation  of  the  Heating  Value  from  Chemical  Analysis — 
If  an  ultimate  analysis  is  available,  the  heating  value  of  a  coal 


246  GAS  AND  FUEL  ANALYSIS 

may  be  calculated  with  fair  accuracy  from  the  Dulong  formula 
which  is  usually  given  as 


Calorific  power  = 


8080  C  +  34460  (H  -  g)  +  2500  S 
100 


where  C,  H,  O  and  S  represent  the  respective  percentages  of 
these  various  elements  shown  by  the  analysis.  This  formula 
gives  results  in  Calories  per  kilogram  which  when  multiplied  by 
1.8  are  converted  into  British  thermal  units  per  pound.  Tests 
of  57  coals  made  by  the  U.  S.  Geological  Survey1  show  an  average 
error  of  87.5  calories  in  the  calculated  result  and  a  maximum 
error  of  312  calories.  Inasmuch  as  it  is  much  simpler  to  deter- 
mine the  calorific  value  directly  than  to  make  an  ultimate  analy- 
sis, the  value  of  this  formula  has  come  to  lie  largely  in  its  confir- 
mation of  the  correctness  of  the  ultimate  analysis. 

A  formula  which  would  correlate  proximate  analysis  and 
heating  value  would  be  much  more  useful,  but  on  account  of  the 
variable  composition  of  the  volatile  matter  in  different  types  of 
coal  no  general  formula  can  be  devised  which  will  fit  all  cases. 
The  combustible  matter  of  coal  from  a  given  seam  is,  however, 
quite  constant  in  composition  and  after  its  value  has  been  experi- 
mentally determined  this  figure  may  be  used  with  considerable 
accuracy  as  a  basis  for  the  calculation  of  the  heating  value  of 
similar  coals  whose  moisture  and  ash  content  are  known. 

1  U.  S.  G.  S.,  Professional  Paper  48  (1906);  Bulletin  382  (1909)  p.  24. 


APPENDIX 


247 


TABLE  I.— SATURATION  PRESSURE  OF  WATER  VAPOR 


From  0-50°  C. 
.  (4),  31,  731 

Temp. 


in  millimeters  of  mercury.     Scheel  and  Heuse,  Ann. 
(1910). 


mm.  Hg. 


Temp. 


mm.  Hg. 


0 

4.579 

26 

25.217 

1 

4.926  . 

27 

26  .  747 

2 

5.294 

28 

28.358 

.  3 

5.685 

29 

30.052 

4 

6.101 

30 

31.834 

5 

6.543 

31 

33  .  706 

6 

7.014 

32 

35.674 

7 

7.514 

33 

37.741 

8 

8.046 

34 

39.911 

9 

8.610 

35 

42.188 

10 

9.210 

36 

44.577 

11 

9.845 

37 

47  .  082 

12 

10.519 

38 

49.708 

13 

11.233 

39 

52.459 

14 

11.989 

40 

55.341 

15 

12.790 

41 

58.36 

16 

13.637 

42 

61.52 

17 

14.533 

43 

64.82 

18 

15.480 

44 

68.28 

19 

16.481 

45 

71.90 

20  '• 

17.539 

46 

75.67 

21 

18.655 

47 

79.62 

22 

19.832 

48 

83.74 

23 

21.074 

49 

88.05 

24           22.383 

50 

92.54 

25 

23.763 

248 


GAS  AND  FUEL  ANALYSIS 


TABLE  II.— REDUCTION  OF  GAS  VOLUMES  TO  0°  AND  760  MM. 
MERCURY  PRESSURE  AND  DRYNESS 

If  the  gas  is  already  dry  the  reduction  formula  is 


V  o        -|     i     f\/\< 


1  +  . 00367  t  760 

where  t  is  the  temperature  and  h  the  barometric  pressure  corresponding  to 
the  volume  V. 

If  the  gas  is  saturated  with  moisture  there  must  be  deducted  from  the 
oberved  barometric  reading  the  value  e  for  the  vapor  pressure  of  water 
corresponding  to  the  temperature  t  as  given  in  Table  I.  The  reduction 
formula  then  becomes 


Vo- 


h-e 


1  +  .00367  t    760 


The  following  table  gives,  the  values  for  l+0.00367t  for   each   degree 
from  0°  to  50°  C. 


l+0.00367t 


l+0.00367t 


0 

1.00000 

26 

1.09542 

1 

1.00367 

27 

1.09909 

2 

1.00734 

28 

1  .  10276 

3 

1.01101 

29 

1  .  10643 

4 

1.01468 

30 

1..  11010 

5 

1.01835 

31 

1.11377 

6 

1.02202 

32 

1  .  11744 

7 

1.02569 

33 

1.12111 

8 

1.02936 

34 

1  .  12478 

9 

1.03303 

35 

1  .  12845 

10 

1.03670 

36 

1  .  13212 

11 

1.04037 

37 

1  .  13579 

12 

1.04404 

38 

1  .  13946 

13 

1.04771 

39 

1.14313 

14 

1.05138 

40 

1.14680 

15 

1.05505 

41 

1.15047 

16 

1.05872 

42 

1.15414 

17 

1.06239 

.  43 

1  .  15781 

18 

1.06606 

44 

1.16148 

19 

1.06973 

45 

1.16515 

20 

1.07340 

46 

1.16882 

21 

.07707 

47 

1  .  17249 

22 

.08074 

48 

1.17616 

23 

.08441 

49 

1.17983 

24 

.08808 

50 

1  .  18350 

25 

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OS  1-1 


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0  0  2 

o  o  o 


SS8 


o  o  o 
odd 


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o  o  o 


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CO    CO    t> 


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r^  o  CN 

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O3   CN    rj* 

1-1    CN    CN 
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iO   X   O 

^H     ^H     CN 

O    O    O 


CN    TJ4    CO 

O   O   O 


,  3HnXVH3dK3X 
251 


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CO1>I>1>-OOOOOOOOOOOOOOOOQOOOO5O5O5O5O5 

l^OOOOOOOOOOOOO5O5O5O5O5O5O5O5O5O5O5O5 

252 


s  $ 

I  bi, 


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SI 


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— 


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os       co 

00  •  rH  IO  00 

CO  CO  OS 

CO  »O  00  rH 

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•   •   •   •    CO  CO  OS  CO 
^  !>•  O  CO 

rH  IO  OS  CO  10 

rH  rH 

co  t>»  co  co  co 


jiy 


rH    TJH     00    rH 


CO   O  CO   CO   00 


CO    OS    CO    CO    O5    rH 


OS   <N    CO   Oi 


CO    O 


CO  00  CO  CO  OS  <N 

rH  rH  rH  CO 


00  rH  Tt<  CO  00 


00   O 
<N   CO 


QO  rH  TfH  t^  OS  rH 
rH  CO  <M  CO  C<1  CO 


CO   I-H    CO 


i-HCOO 
'-H'-i(M 


(NOOCOOO 


COOO(MiOOOOCO 
'-H'-i(N(M(MCOCO 


1-1  CO  O 


O  CO  T^ 

CO  CO  CO 


CO 
CO  CO 


00  CO  00  CO  CO  OS  CO 

rH  rH  CO  CO  CO  CO 


^OOOOOSOSOOrH 
rH     rH    rH 

253 


iO  O 

rH  (^ 


254 


GAS  AND  FUEL  ANALYSIS 


TABLE  V.— MEAN  SPECIFIC  HEATS  OF  GASES  AT  CONSTANT 

PRESSURE  IN  B.T.U.  PER  CUBIC  FOOT  AT  60°  F.  AND  30  IN. 

OF  MERCURY  CALCULATED  FOR  THE  INTERVAL 

60°  F.-T 


T, 
deg.  F. 

Carbon  dioxide 

Water  vapor 

Nitrogen,  oxygen  and 
other    diatomic    gases 

200 

0.0237 

0.0220 

0.0174 

400 

0.0246 

0.0220 

0.0175 

600 

0.0253                      0.0221 

0.0177 

800 

0.0260                      0.0222 

0.0178 

1000 

0.0268                      0.0224 

0.0180 

1200 

0.0275                      0.0226 

0.0181 

1400 

0.0282                      0.0229 

0.0183 

1600 

0.0287                      0.0232 

0.0184 

1800 

0.0292                      0.0236 

0.0186 

2000 

0.0298                      0.0240 

0.0187 

2200 

0.0302                      0.0245 

0.0189 

2400 

0.0306 

0.025C 

0.0190 

2600 

0.0309 

0.0256 

0.0192 

2800 

0.0312 

0.0263 

0.0194 

3000 

0.0314 

0.0270 

0.0196 

TABLE  VI.— MEAN  SPECIFIC  HEATS  OF  GASES  AT  CONSTANT 
PRESSURE  IN  B.T.U.  PER  POUND  CALCULATED  FOR 
THE  INTERVAL  60°  F.-T 


T 

Carbon  dioxide 

Water  vapor 

Nitrogen 

200°  F. 

0.2067 

0.4653 

0.2365 

400°  F. 

0.2143                      0.4657 

0.2386 

600°  F. 

0.2216                      0.4673 

0.2407 

800°  F. 

0.2285 

0.4698 

0.2428 

1000°  F. 

0.2348 

0.4735 

0.2449 

1200°  F. 

0.2406 

0.4782 

0.2470 

1400°  F. 

0.2462 

0.4841 

0.2491 

1600°  F. 

0.2512 

0.4910 

0.2512 

1800°  F. 

0  .  2559 

0  .  4990 

0.2534 

2000°  F. 

0.2601 

0.5081 

0.2555 

2200°  F. 

0.2638 

0.5182 

0.2576 

2400°  F. 

0.2670 

0.5294 

0.2597 

2600°  F. 

0.2698 

0.5420 

0.2618 

2800°  F. 

0.2722 

0  .  5557 

0.2639 

3000°  F. 

0.2742 

0.5702 

0.2660 

APPENDIX 


255 


TABLE  VII.— VOLUME  OF  WATER  VAPORS  TAKEN  UP  BY  ONE 
CUBIC  FOOT  OF  AIR  WHEN  SATURATED  AT  VARIOUS 
TEMPERATURES 


Temperature 


Cubic  feet  of  water  vapor 


0°F. 
12°  F. 
22°  F. 
32°  F. 
42°  F. 
52°  F. 
62°  F. 
72°  F. 
82°  F. 
92°  F. 
102°  F. 


0.001 
0.002 
0.004 
0.006 
0.009 
0.013 
0.019 
0.027 
0.038 
0.053 
0.073 


TABLE  VIII.— COMPARISON  OF  THE  BAUME  SCALE  FOR 

LIQUIDS  LIGHTER  THAN  WATER  AND  SPECIFIC 

GRAVITIES 


Degrees 
Baum6 

Specific 
gravity 

Degrees 
Baum6 

Specific 
gravity 

Degrees 
Baum6 

Specific 
gravity 

10 

1.0000 

36 

0.8433 

62 

0.7290 

11 

0.9929 

37 

0.8383 

63 

0.7253 

12 

0.9859 

38 

0.8333 

64 

0.7216 

13 

0.9790 

39 

0.8284 

65 

0.7179 

14 

0.9722 

40 

0.8235 

66 

0.7142 

15 

0.9655 

41 

0.8187 

67 

0.7106 

16 

0.9589 

42 

0.8139 

68 

0.7070 

17 

0.9523 

43 

0.8092 

69 

0.7035 

18 

0.9459 

44 

0.8045 

70 

0.7000 

19 

0.9395 

45 

0.8000 

71 

0.6990 

20 

0.9333 

46 

0.7954 

72 

0.6956 

21 

0.9271 

47 

0.7909 

73, 

0.6923 

22 

0.9210 

48 

0.7865 

74 

0.6889 

23 

0.9150 

49 

0.7821 

75 

0.6829 

24 

0.9090 

50 

0.7777 

76 

0.6823 

25 

0.9032 

51 

0.7734 

77 

0.6789 

26 

0.8974 

52 

0.7692 

78 

0.6756 

27 

0.8917 

53 

0.7650 

79 

0.6722 

28 

0.8860 

54 

0.7608 

80 

0.6666 

29 

0.8805 

55 

0.7567 

81 

0.6656 

30 

0.8750 

56 

0.7526 

82 

0.6619 

31 

0.8695 

57 

0.7486 

83 

0.6583 

32 

0.8641 

58 

0.7446 

84 

0  .  6547 

33 

0.8588              59 

0.7407 

85 

0.6511 

34 

0.8536 

60 

0.7368 

90 

0.6363 

35 

0.8484 

61 

0.7329 

95 

0.6222 

SUBJECT  INDEX 


PAGE 

Absorption  methods  in  gas  analysis 28-40 

Acetylene, 29 

diffusion  of 80 

estimation  of 81 

as  inhibiting  catalyzer 32 

solubility  of  in  water 81 

Accuracy  of  coal  analysis 212 

of  coal  sampling 191 

of  explosion  analysis 46 

of  photometric  work 131 

of  technical  gas  analysis 27 

Air  and  chimney  gases,  volume 142 

determination  of  relative  humidity 107 

impure  affecting  candle-power 131 

volume  per  pound  of  carbon  in  combustion 143 

and  water  vapor  table  of  volumes 255 

Air-drying  coal 195 

Alcohol  as  fuel,  see  liquid  fuel. 

Alkaline  pyrogallate,  reagent  for  oxygen 33 

Ammonia,  estimation  in  gas 169 

Argon  group 86 

Arsenious  oxide  as  reagent 69 

Ash  in  coal 202 

accuracy  of  analysis 212 

Aspirators 5 

Atkinson  method  for  sulphur  in  coal 207 

Average  sample  of  gas 8 

Bar  photometer 1 14 

Barium  hydroxide  as  reagent  for  carbon  dioxide 80 

Baume  scale  for  liquids  lighter  than  water,  table 255 

Benzene,  estimation 159 

Benzine  as  inhibiting  catalyzer 32 

Benzoic  acid  as  standard  in  coal  calorimetry 234 

Blast-furnace  gases,  sampling 136 

Bomb  calorimeter,  details 215 

manipulation 219 

see  also  heating  value  of  coal 214 

Bray's  No.  7  slit  union  burner 123 

British  thermal  unit  defined 99 

Bromine  water,  reagent 29 

17  257 


258  SUBJECT  INDEX 

PAGE 

Bulbed  gas  burette  for  exact  analysis 75 

Bunsen  photometric  screen 123 

Bunte's  gas  burette 65 

Burners,  standard  gas 122 

Butylene  (iso),  initial  combustion  temperature. 54 

Calculation  of  candle-power 130 

explosion  analysis 47 

heat  lost  in  chimney  gases 146 

heating  value  of  coal 227 

heating  value  of  gas 100 

heating  value  of  gas  from  chemical  composition Ill 

Calibration  of  bulbed  gas  burette 79 

gas  burette 22 

wet  gas  meter 89 

Calorimeters  for  gas,  requirements 87 

see  heating  value, 
see  bomb, 
see  Parr. 

Thompsons 238 

using  oxygen  under  low  pressure 238 

water  value  of 232 

Calory  defined .  99 

Candle,  English  parliamentary 115 

international 116 

balance 117 

Candle-power,  accuracy  of  estimation 131 

bar  photometer 114 

Bunsen  screen 123 

calculations 130 

decreasing  significance  of 132 

details  of  test 128 

Edgerton  Standard 121 

Elliot  lamp 121 

equipment  of  photometer  bench 126 

flicker  photometer. . . 126 

gas  meter 126 

humidity  of  ah* 130 

impure  air 131 

jet  photometer 131 

Leeson  star  disc 123 

Lummer-Brodhun  photometric  screen 123 

method  of  rating 113 

of  illuminating  gas 113 

photometer  room 130 

saturating  water  of  meter 126 

secondary  standards 121 


SUBJECT  INDEX  259 

PAGE 

Candle-power,  setting  consumption  of  gas 129 

solubility  of  illuminants 126 

standard  gas  burners 122 

standard  lights 115 

table  photometer 114 

types  of  photometer 114 

units  of  intensity 115 

use  of  Hefner  lamp 117 

use  of  pentane  lamp 120 

use  of  standard  candles 116 

Capillary  tube  preventing  explosion 50 

Carbon  dioxide 28 

determination  of 80 

formation  of 139 

table  of  specific  heats 254 

Carbon  monoxide  causing  change  in  blood 82 

in  chimney  gas 141 

combustion  with  copper  oxide 54 

and  cuprous  chloride 35 

determination  of / 35 

estimation  of  by  cuprous  chloride 82 

estimation  of  by  iodine  pentoxide 82 

evolved  from  pyrogallate  solution 33 

explosion  analysis 48 

fractional  combustion  with  pallodinised  asbestos  ...     52 

hydrogan  and  methane  simultaneous  explosion 48 

incomplete  absorption 35 

initial  combustion  temperature 54 

quiet  combustion  with  oxygen - 51 

Carbon,  total,  in  coal 209 

Carbonates  in  coal  ash 202 

Carbonic  acid,  see  carbon  dioxide. 
Carbonic  oxide,  see  carbon  monoxide. 

Carburetted  water  gas 159 

Caustic  soda,  reagent 28 

Chemical  analysis  of  coal,  see  coal  analysis . 

Chemical  analysis  and  heating  value  of  coal 245 

•Chemical  composition  of  gas  and  heating  value Ill 

Chimney  gas 139 

calculation  for  loss  of  heat  in 145 

carbon  monoxide  in 145 

change  in  composition  in  contact  with  water 7 

effect  of  hydrogen  of  coal  on  composition 140 

interpretation  of  analysis 147 

loss  of  heat  in ^ 147 

loss  of  heat  due  to  moisture » 144 

volume..  .    143 


260  SUBJECT  INDEX 

PAGE 

Chimney  gases,  and  volume  of  air 142 

Chollar  tubes 67 

Clinkering  properties  of  ash 203 

Coal  analysis 193 

accuracy 212 

air-drying 195 

ash 202 

deterioration  of  samples 198 

fixed  carbon 203 

grinding  sample 196 

hydrogen 209 

method  of  reporting 211 

moisture 198 

nitrogen 210 

oxygen 211 

phosphorus 211 

preliminary  examination  of  sample 194 

preserving  sample 198 

sulphur 204 

total  carbon 209 

ultimate  analysis 209 

volatile  matter .   200 

Coal,  ash  in 202 

briquetting  sample  for  bomb  calorimeter 218 

changes  on  air-drying 195 

changes  after  mining 189 

chemical  analysis 193 

combined  water  in 145 

difference  in  composition  of  lump  and  fine 182 

fixed  carbon  in 203 

Coal  gas 159 

chemical  composition 157 

see  illuminating  gas. 

Coal,  grinding 197 

gross  and  net  heating  values 237 

heating  value  of,  see  heating  value. 

moisture  in 198 

precautions  in  crushing 187 

proximate  analysis 193 

Coal  sampling 181 

accuracy 189 

a  scoopful  as  a  sample 184 

difference  in  composition  of  lump  and  fine  coal 182 

from  cars 186 

from  wagons 186 

influence  of  lumps  of  slate 185 

in  the  mine. .  .  •  •    186 


SUBJECT  INDEX  261 

PAGE 

Coal  sampling,  mixing 188 

picking  a  sample 186 

preparation  of  sample 187 

preservation  of  sample 188 

reliability  of  samples 192 

size  of  sample *. 184,  191 

sulphur  in 204 

substance 211 

tar  as  fuel,  see  liquid  fuel . 

ultimate  analysis 209 

variations  in  results 191 

volatile  matter 200 

washing 213 

Coke  oven  gas 159 

Colloidal  palladium  as  reagent  for  hydrogen 38 

Combustion  with  copper  oxide,  accuracy  of 86 

fractional  with  copper  oxide 54 

fractional  with  palladinised  asbestos 51 

methods  in  gas  analysis 41 

quiet  of  air  and  gas 49 

tube  for  copper  oxide 55 

Contrast  photometer 125 

Conversion  factors  for  heating  value  of  gas 100 

Copper  oxide,  fractional  combustion  with 54 

quartz  combustion  tube 55 

Corrections  for  temperature  and  pressure  of  gas 71,  90 

Corrections  for  temperature  and  pressure,  tables 248-252 

Cubic-foot  bottle 89 

Cubic  foot  of  water,  weight  of 89 

Cuprous  chloride  acid  solution 35 

ammoniacal  solution 36 

and  carbon  monoxide 34 

preservation  of 35 

as  reagent  for  carbon  monoxide 82 

as  reagent  for  oxygen 34 

regeneration 36 

Cyanogen  compounds  in  gas 170 

Diffusion,  errors  due  to 80 

prevention  of 80 

Dulong  formula 246 

Edgerton  Standard  lamp 121 

Electrical  precipitation  of  suspended  particles 137 

Elliot  lamp 121 

Eschka  method  for  sulphur  in  coal 204,  205 

Ethane,  analysis  by  combustion 57 


262  SUBJECT  INDEX 

PAGE 

Ether  as  inhibiting  catalyzer 32 

Ethylene 29 

initial  combustion  temperature 54 

as  inhibiting  catalyzer 29 

Exact  gas  analysis 70 

absorption  methods 80 

bulbed  burette  for 75 

burette  for 73 

manipulation  of  burette 77 

Excess  oxygen  over  explosion  requirements 48 

Explosive  ratios 45,  84 

Explosion  analysis,  accuracy 46 

apparatus 41 

manipulation 44 

Explosion  methods  in  gas  analysis 41 

for  hydrogen 46 

for  methane 46 

Explosion,  not  prevented  by  capillary  tube 50,  53 

Explosion  pipette 41 

screen 43 

Explosion,  simultaneous  of  hydrogen  and  methane 46 

simultaneous  of  hydrogen  and  methane  and  carbon  mon- 
oxide    48 

Filtering  media  for  solid  particles  in  gas 136 

Fjxed  carbon  in  coal  analysis 203 

i-Flash  point  of  oils 180 

Flicker  photometer 126 

Form  of  record  of  gas  analysis 59 

(Beating  value  of  gas 100 

Formation  of  producer  gas 149 

Fractional  combustion  with  copper  oxide 54 

palladinised  asbestos   51 

Fuels,  liquid  see  liquid  fuels. 

Fuming  sulphuric  acid,  reagent 29 

Gas  analysis,  absorption  methods 28-40 

accuracy  of  technical 27 

apparatus — Allen-Moyer  modification 64 

Bunte's 65 

Chollar's 67 

Orsat's 62 

Schlosing  and  Hollands 61 

various  types 61 

calibration  of  burette 22,  79 

carbon  dioxide 28,  80 

carbon  monoxide 34,  82 


SUBJECT  INDEX  263 

PAGE 

Gas,  Analysis,  combustion  methods 41 

corrections  for  temperature  and  pressure 71 

details  of  manipulations 25 

drawing  sample  into  burette 18 

exact  methods 70 

exact  methods,  manipulation  of  burette 77 

by  explosion,  calculations 47 

by  explosion,  explosive  ratio 45 

by  explosion,  hydrogen 46 

by  explosion,  manipulation 44 

explosion  methods 41 

explosion,  methane  and  hydrogen 46 

by  explosion,  oxidation  of  nitrogen '45 

form  of  record 59 

by  fractional  combustion  with  copper  oxide 54 

by  fractional  combustion  with  palladinised  asbestos.  ...  51 

the  gas  burette 16 

gas  pipettes • 24 

general  methods 14 

general  scheme 38 

hydrogen •. 83 

manipulation 19 

manipulation  of  burette 24 

measurement  of  volume 21 

methane 85 

nitrogen 58 

defines 81 

order  of  absorptions 39 

oxygen ...   30,  82 

by  quiet  combustion  of  oxygen  and  gas 49 

reduction  of  volume  to  standard  conditions 72 

saturating  burette  water 18 

transferring  gas  from  holder,  see  also  under  individual 

gases 19 

unsaturated  hydrocarbons 28,  81 

wiring  rubber  connections 19 

Gas  burette,  calibration 22,  79 

bulbed  for  exact  gas  analysis 75 

with  compensator  for  temperature  and  pressure 73 

description 15 

for  exact  gas  analysis 73 

for  exact  analysis,  manipulation 78 

manipulation,  standard 25 

see  gas  analysis. 

Gas  burners,  standard 122 

Gns  calorimeters 87 

adjusting  for  a  test 97 


264  SUBJECT  INDEX 

PAGE 

Gas  calorimeters,  automatic Ill 

control  of  water 91 

Doherty's 110 

Graefe's 110 

Hempel's 110 

Junkers 92 

measurement  of  water  heated 92 

Parr's 110 

recording Ill 

thermometers,  see  heating  value  of  gas 91 

Gas,  calculated  heating  value Ill 

candle  power  of 113 

candle  power  of,  see  candle  power. 

estimation  of  suspended  particles 133 

estimation  of  suspended  tar  and  water 137 

heating  value  of,  see  heating  value. 

holder  for  samples 12 

holder,  transferring  gas  from 20 

illuminating,  see  illuminating  gas. 

influence  of  bends  in  main  on  suspended  particles 134 

main,  point  of  sampling. . .  ^ 135 

mains,  distribution  of  suspended  particles  in  cross  section 133 

mains,  influence  of  bends 134 

mean  velocity  in  cross  section  of  main 134 

meter  for  candle-power  determinations 126 

wet 88 

wet,  calibration 89 

natural,  see  natural  gas 156 

percentage  used  for  heating  and  lighting 132 

pipettes 24 

producer 149 

producer,  efficiency 155 

producer,  see  producer  gas. 

sampling  apparatus 9 

sampling,  filters  for  solid  particles 136 

sampling,  see  sampling  gas. 

samples,  shipment  of 13 

sampling  tanks,  saturation  of  water 8 

^specific  gravity  of 171 

suspended  particles  in 134 

table  of  specific  heats 254 

velocity  in  sampling  tube 135 

volume,  corrections  for  temperature  and  pressure 90 

i/volume  measurement,  errors 103 

volumes,  tables  of  reduction 248-252 

Gases,  change  in  volume  in  combustion 139 

from  chimneys 139 


SUBJECT  INDEX  265 

PAGE 

Guises,  solubility  in  water 6 

U"Gasoline  from  natural  gas 172 

Grinding  coal  samples. . .  , 196 

Gross  heating  value  of  gas 101 

Gross  heating  value  of  coal 237 

Heating  value  of  coal,  accuracy  of  results 236 

the  bomb  calorimeter 214 

calculated  from  chemical  analysis 245 

in  calorimeters  using  low-pressure  oxygen 238 

in  calorimeter  using  chlorate  and  nitrate 238 

corrections  for  combustion  of  iron  wire 231 

corrections  for  oxidation  of  sulphur 230 

corrections  for  oxidation  of  nitrogen 229 

details  of  bomb  calorimeter 215 

gross  and  net  heating  values 237 

manipulation  of  bomb  calorimeter 219 

by  Parr  calorimeter 238 

Parr  calorimeter  details 242 

preparation  of  sample 218 

radiation  correction 223 

reduction  to  constant  pressure 231 

sample  of  record 227 

thermometer  corrections 223 

thermometers 218 

water  value  of  calorimeter 232 

Heat  lost  in  chimney  gases 143,  145,  147 

Heating  value  of  gas 87 

accuracy  of  determination  of 102 

calibration  of  meter 89 

calculated  from  chemical  composition Ill 

calculation  of  results 99 

continuous  flow  calorimeters 87 

control  of  water 91 

corrections  for  temperature  and  pressure 71 

corrections  for  unsaturated  air 106 

conversion  factors 100 

corrections  to  observed  heat  to  get  total  heat  value  107 

description  of  test 98 

Doherty's  calorimeter 110 

errors  due  to  sensible  heat  in  combustion  gases .  .    104 

errors  due  to  uncondensed  water  vapor 104 

errors  in  determining  mass  of  water  heated 104 

errors  in  temperature  measurement 103 

errors  in  registration  of  gas  volume 103 

form  of  record 100 

Graefe  calorimeter ..  .    110 


266  SUBJECT  INDEX 

PAGE 

Heating  value  of  gas,  gross  value 101 

Hempel's  calorimeter 110 

Junkers'  calorimeter ....  92 

loss  of  heat  by  radiation 107 

measurement  of  mass  of  water 91 

measurement  of  temperature 91 

meter  used 88 

method  of  reporting 100 

net  value 101 

non-continuous  calorimeters 110 

Parr  calorimeter 110 

preliminaries  of  test 95 

recording  calorimeters Ill 

saturating  water  in  meter 98 

total  accuracy 107 

Heating  value  of  liquid  fuels 175 

pure  materials  used  in  calorimetry 234 

Hefner  lamp 117 

Hefner  unit  of  light '. 116 

Humidity  of  air  affecting  candle-power 130 

determination 107 

relative,  tables 252,  253 

Hydrochloric  acid,  removal  of  from  gases 80 

Hydrogen  absorption  by  palladium 36 

accuracy  of  estimation  affected  by  explosive  ratio 84 

carbon  monoxide  and  methane,  simultaneous  explosion.  ...  48 

in  coal 209 

in  coal  affecting  composition  of  chimney  gas 140 

combustion  with  copper  oxide 54 

comparison  of  methods  for  determination  of 84 

combustion  with  oxygen 84 

determination  of,  by  palladous  chloride 37 

estimation  of 83 

explosion  analysis 46,  84 

error  in  estimation  due  to  oxides  of  nitrogen 84 

fractional  combustion  with  palladinized  asbestos .  51 

initial  combustion  temperature 54 

and  methane  by  explosion 46 

and  palladium,  inhibiting  catalyzers 36 

quiet  combustion  with  air 49 

Hydrogen  sulphide   arsenious  acid  as  reagent 69 

in  illuminating  gas 161 

as  inhibiting  catalyzer 32 

with  carbon  dioxide 28 

removal  of  from  gases 80 

Hydrosulphite  as  reagent  of  oxygen 34 

Hydrometer,  Baume,  for  liquids  lighter  than  water,  table 255 


SUBJECT  INDEX  267 

PAGE 

Illuminating  gas 156 

benzene 159 

candle  power  of 113 

change  in  composition  in  contact  with  water 7 

chemical  composition 157 

estimation  of  ammonia 169 

estimation  of  cyanogen  compounds 170 

estimation  of  suspended  tar  and  naphthalene 166 

hydrogen  sulphide  in 161 

naphthalene  estimation 164 

sampling 156 

scheme  of  analysis 157 

specific  gravity  of .  171 

total  sulphur  compounds  in 162 

typical  analyses 158 

Illuminants,  solubility  of 126 

Incomplete  combustion  in  chimney  gases 141 

Inhibiting  catalyzers  for  oxygen  and  phosphorous 32 

Initial  combustioo  temperatures  of  various  gases 54 

International  candle 116 

Iodine  pentoxide  as  reagent  for  carbon  monoxide 82 

Iron,  heat  of  combustion .  231 

Jet  photometers 131 

Junkers'  gas  calorimeter 92 

Junkers'  calorimeter  for  liquid  fuels 177 

Junkers'  recording  calorimeter Ill 

Kjehldahl  method  for  nitrogen  in  coal : 210 

Leeson  star  disc 123 

Liquid  fuels 174 

flash  point : .180 

i^neating  value 175 

Junkers'  calorimeter  for , 177 

moisture 178 

proximate  analysis  of 179 

sampling 174 

specific  gravity 178 

suspended  solids  in 179 

Lubricant  for  stopcocks 17 

Lummer-Brodhun  contrast  photometer 125 

photometric  screen 123 


kM< 


easurement  of  gas  volume 21 

Meter  for  candle-power  determinations , 126 

Meter,  wet  gas 88 


268  SUBJECT  INDEX 

PAGE 

Methane,  accuracy  of  estimation  affected  by  explosive  ratio 85 

carbon  monoxide  and  hydrogen,  simultaneous  explosion.  ...  48 

combustion  with  copper  oxide 54 

estimation  of,  by  explosion 85 

error  in  estimation  due  to  oxides  of  nitrogen 85 

explosion  analysis 46,  85 

and  hydrogen  by  explosion 46 

initial  combustion  temperature 54 

quiet  combustion  with  air 49 

Metropolitan  No.  2  burner 123 

Mine  sampling  of  coal 186 

Moisture  in  air,  see  humidity . 

in  coal 198 

in  coal,  accuracy  of  analysis 212 

in  gas,  calculation  for 72 

in  liquid  fuels 178 

in  tar 179 

Naphthalene  estimation  in  purified  gas. 164 

estimation  in  tar 167 

estimation  in  purified  gas 165 

as  standard  in  coal  calorimetry 234 

Natural  gas 156 

analysis 172 

gasoline  vapors  in 173 

typical  analyses 173 

Net  heating  value  of  coal 237 

of  gas 101 

Nitrogen  in  gas  analysis 58,  86 

in  coal. 210 

oxidation  in  bomb  calorimeter 230 

table  of  specific  heats 254 

Olefines 29 

Estimation  of  mean  composition 81 

Orsat  apparatus 62 

Oven  for  air-drying  coal  samples 196 

Oxides  of  nitrogen  formed  in  explosion 44 

formed  in  combustion 51 

Oxidation  of  nitrogen,  error  caused  by 45 

causing  error  in  estimation  of  hydrogen 84 

Oxygen,  always  present 31 

analysis  of  commercial 32 

in  coal 211 

concentrated  and  phosphorus 32 

determination  of  by  alkaline  pyrogallate 33 

determination  of  by  phosphorus 30 


SUBJECT  INDEX  269 

PAGE 

Oxygen,  estimation  by  explosion  with  hydrogen 34 

estimation  by  metallic  copper 34 

estimation  of  by  phosphorus 82 

in  excess  of  explosion  requirements 48 

and  phosphorus,  inhibiting  catalyzers 32 

and  phosphorus  at  low  temperatures 31 

by  pyrogallate  solution 33 

sodium  hydrosulphite  as  reagent 34 

table  of  specific  heats 254 

Palladinised  asbestos 51 

Palladinised  copper  oxide  for  fractional  combustion 54 

Palladium,  colloidal  as  reagent  for  hydrogen . » 38 

and  hydrogen,  inhibiting  catalyzers 36 

as  reagent  for  hydrogen 36 

Palladous  chloride  as  reagent  for  hydrogen 36 

Parr  calorimeter 238 

accuracy 245 

corrections 244 

for  heating  value  of  liquid  fuels 176 

operation 242 

preparation 240 

Pentane,  analysis  by  combustion '. 57 

Pentane  lamp 120 

Permanganate  as  reagent  for  reducing  gases 80 

Peroxide  calorimeter 239 

Peroxide 242 

method  for  sulphur  in  coal 206 

Petroleum  compounds,  flash  point 180 

moisture  in 178 

see  also  liquid  fuels 174 

Phosphorus  in  coal 211 

as  indicator  of  absence  of  unsaturated  hydrocarbons.    29,  31,  81 

inhibiting  catalyzers 30 

and  oxygen,  inhibiting  catalyzers 32 

and  oxygen  at  low  temperatures 31 

to  be  protected  from  light 30 

Phosphorus,  reagent  for  oxygen 30,  82 

Photometer,  bar  type 114 

bench  and  equipment 126 

room 130 

table  type 114 

Photometric  units 115 

Photometry,  see  candle-power. 

Pintsch  gas 29 

Pipette  for  explosion  analysis 41 

Pipettes,  gas 24 


270  SUBJECT  INDEX 

PAGE 

Portable  gas  analysis  apparatus 61-69 

Pressure  of  gas,  corrections  for 71 

Pressure  of  water  vapor,  table 247 

Producer  gas  analysis 151 

calculation  of  volume 153 

efficiency  of  producer 155 

formation 149 

heating  value 153 

interpretation  of  analysis 152 

sampling 151 

sensible  heat  in 154 

typical  analyses 150 

Propylene,  initial  combustion  temperature 54 

Proximate  analysis  of  coal 193 

Proximate  analysis  of  liquid  fuels 179 

Psychrometer 107 

Pyrites,  separation 213 

Pyrogallol,  evolution  of  carbon  monoxide 33 

Pyrogallol,  reagent  for  oxygen 33,  82 

Quartz  combustion  tube  for  copper  oxide 55 

Quartz  combustion  tube  with  platinum  spiral 49 

Radiation  corrections  in  calorimetry 223 

Dickinson  formula 228 

Regnault-Pf aundler  formula 224 

Radiation  loss  in  gas  calorimeter 107 

Reduction  of  gas  volumes  to  0°  and  760  mm.  table 248 

Reduction  of  gas  volumes  to  60°  F.  and  30  inches,  table 249-251 

Regnault-Pf  aundler  formula  for  radiation  corrections 225 

Rubber  connections,  danger  of  in  gas  analysis 19 

Sampling  blast  furnace  gas .  136 

crude  illuminating  gas  for  naphthalene 166 

coal 181 

see  also,  coal  sampling. 

gas,  apparatus 9 

aspirators 5 

collecting  a  representative  instantaneous  sample 11 

collection  of  an  average  sample 8 

continuous  apparatus 10 

difficulties 1 

errors  due  to  solubility 7 

from  main 135 

illuminating 156 

liquid  fuels 174 

materials  for  sampling  tubes 2 


SUBJECT  INCEX  271 

PAGE 

Sampling,  method 3 

multiple  sampling  tube 3 

problem  of  fair  sample 1 

producer,  gas 151 

shipment  of  samples ; 13 

solubility  of  gases  in  water 6 

storing  the  sample -11 

tube,  proper  velocity  of  gas 135 

Saturating  burette  water  with  gas , 18 

water  in  gas  meter 98 

Saturation  of  water  in  gas  sampling  tanks 8 

pressure  of  water  vapor,  table 247 

Slate  as  cause  of  error  in  coal  sampling 185 

separation 213 

Sling  psychro meter 107 

Sodium  hydrosulphite  as  reagent  for  oxygen 34 

Sodium  hydroxide,  reagent 28 

Sodium  peroxide,  care  of 242 

Solubility  of  gases  in  water 6 

Specific  gravity  compared  with  the  Baume  scale  for  liquids  lighter  than 

water,  table 255 

of  gas 171 

ofliquidfuels .    178 

Specific  heat  of  materials  used  in  calorimeters 233 

of  gases,  table  of 254 

Standard  gas  burners 122 

Standard  conditions  for  gas 90 

Standard  light 115 

Stopcocks,  care  of 17 

Storage  of  gases • 11 

Sugar  as  standard  in  coal  calorimetry 234 

Sugg  D  burner 122 

F  burner 122 

Sulphates  in  coal  ash 202 

Sulphur  in  coal 204 

accuracy  of  analysis 212 

Eschka  method 205 

peroxide  method 206 

Atkinson  method 207 

Parr's  photometric  method 208 

Sulphur  compounds  in  illuminating  gas 162 

Sulphur  dioxide  with  carbon  dioxide 28 

removal  of  from  gases 80 

Sulphur,  oxidation  in  bomb  calorimeter »........- 230 

Sulphuretted  hydrogen,  see  hydrogen  sulphide . 

Sulphuric  acid,  fuming  as  reagent 29 


272  SUBJECT  INDEX 

PAGE 

Suspended  particles  in  gas 133 

electrical  precipitation 137 

filtering  medium 136 

point  of  sampling 135 

Suspended  solids  in  liquid  fuels 179 

Suspended  tar  and  water  particles  in  gas 137 

Table  photometer 114 

Tar  as  fuel,  see  liquid  fuel 174 

estimation  of  naphthalene  in 167 

in  illuminating  gas,  estimation 166 

moisture  in 179 

particles  suspended  in  gas 137 

suspended  particles  in  gas  main 134 

Temperature  of  gas,  corrections  for 71 

of  initial  combustion  of  various  gases 54 

measurement,  errors 103 

Thermometer  corrections  for  calorimetry 223 

for  calorimetry 218 

wet  and  dry  bulb 108 

Thompson  calorimeter 238 

Tubes  for  sampling  gases 2 

Ultimate  analysis  of  coal 209 

accuracy 213 

Unsaturated  hydrocarbons 28 

absence  of,  shown  by  phosphorus 29,  81 

estimation  of 81 

estimation  of  mean  composition 81 

separation 81 

Variation  in  coal  samples,  see  coal  sampling. 

Velocity,  varying  in  cross-section  of  gas  main 134 

Volatile  matter  in  coal,  accuracy  of  analysis 212 

Volatile  matter  in  coal 200 

Volume  of  gases,  tables  for  reduction  to  standard  conditions 248-252 

Volume  of  producer  gas 153 

Water,  combined  in  coal 145 

Water  gas,  chemical  composition 158 

Water  value  of  calorimeter,  determination  of 232 

by  direct  weight  of  parts 233 

by  combustion  of  pure  substances 234 

by  method  of  mixtures 235 

electrically 236 

Water  saturated  with  air,  composition  of  the  gases 7 


SUBJECT  INDEX  273 

PAGE 

Water  vapor,  table  of  saturation  pressures 247 

table  of  specific  heats 254 

table  of  volume  for  one  cubic  foot  of  air 255 

uncondensed  in  determining  heat  value  of  gas 104 

weight  per  cubic  foot  of  saturated  air 105 

weight  of  a  liter  at  various  temperatures 221 

weight  per  cubic  foot 89 

Wet  and  dry  bulb  thermometers 108 

Wet  gas  meter 88 

Wiring  rubber  connections 19 

Wiring  stopper  into  burette 74 


INDEX  OF  AUTHORITIES  CITED 

,  PAGE 

Allen  and  Jacobs 178 

Allen  'and  Moyer 64 

American  Chemical  Society,  see  Committe  on  Coal  Analysis. 

American  Gas  Institute 103,  116 

American  Gas  Institute,  see  Committee  on  Calorimetry. 

Atkinson." 207 

Atwater. 215 

Atwater  and  Snell 233 

Badger,  see  Hillebrand. 

Bailey 184,  185,  187,  196 

Barker 204 

Bartlett,  see  Gill.     - 

Berthelot 33,  214 

Blauvelt , 136 

Bleier 75 

Brady 136 

Brodhun,  see  Lummer. 

Bunsen 45,  85,  123,  171 

Bunsen  and  Playfair 70 

Bunte 65,  160 

Burrell 172 

Bureau  of  Mines 174,  191,  195,  209,  210,  211 

Bureau  of  Standards 106,  116,  221,  223 

Campbell 16,  42,  54 

Campbell  and  Hart 36 

Chollar 67 

Cheney 215 

Church 179 

Coleman  and  Smith 164 

Committee  on  Calorimetry 88,  92,  104,  107,  110 

Committee  on  Coal  Analysis 195,  198,  199,  200,  201,  202,  204,  207 

Committee  on  Photometry 130 

Coquillion 49 

Cottrell 137 

Davis,  see  Fieldner. 

Dennis  and  Hopkins 50,  85,  159 

Dickinson 228 

Drehschmidt .  .  . 162 

Doherty 110 

Doyere 70 

Earnshaw 81,  111 

Eschka 204 

274 


AUTHOR  INDEX  275 

PAGE 

Favre  and  Silverman 239 

Fernald  and  Smith 150 

Fieldner  and  Davis 200 

Franzen 34 

Gas  Referees 90,  116,  120,  122 

Gill ' 42,  45 

Gill  and  Bartlett 83 

Graefe 110 

Haber  and  Oechelhaiiser 160 

Harbeck  and  Lunge 161 

Harding ' .  .  .  .  162 

Harcourt 120 

Hart,  see  Campbell. 
Hartman,  see  Paal. 

Heath 205 

Hempel 24,  36,  38,  42,  49,  51,  53,  71,  73,  110,  159,  214 

Hillebrand  and  Badger 198 

Hinman 45 

Heuse,  see  Scheel . 

Holmes 186 

Hopkins,  see  Dennis. 

International  Photometric  Commission 132 

Jacobs,  see  Allen. 

Jaeger 54,  86 

Jenkins .' 162 

Jesse 236 

Jesse,  see  Richards. 

Jones 35 

Junkers 88 

Kinnicutt  and  Sanford 82 

Klumpp 131 

Kroeker 209 

Kuster 164 

Lavoisier 70 

Le  Chatelier,  see  Mallard. 

Leeson 123 

Lord 213 

Lummer  and  Brodhun 123 

Lunge 161 

M-cCarthy,  see  Dennis. 

Mahler 215 

Mallard  and  Le  Chatelier 143 

Morton 159 

Morton,  see  Pennock. 
Moyer,  see  Allen. 

Mueller 170 

Nesmjelow 53 


276  AUTHOR  INDEX 

PAGE 

Nicloux 82 

Noyes  and  Shepherd 48 

Oechelhaiiser,  see  Haber. 

Orsat 34,  62 

Ovitz,  see  Porter. 

Paal  and  Hartmann 37 

Parr, 110,  176,  189,  198,  200,  202,  206,  208,  209,  215,  231,  239,  244 

Pennock  and  Morton 206 

Petterson 73 

Pf  aundler 224 

Playfair,  see  Bunsen. 

Pope 192 

Porter 195 

Porter  and  Ovitz 189 

Ramsburg 161 

Regnault 224 

Regnault  and  Reiset 70 

Reiset,  see  Regnault. 

Richards  and  Jesse 175,  223,  234 

Rolland,  see  Schlosing. 

Rutten 165 

Sanford,  see  Kinnicutt. 

Scheel  and  Heuse 247 

Scheurer-Kestner 239 

Schilling 171 

Schlosing  and  Rolland 61 

Shepherd,  see  Noyes. 
Silverman,  see  Favre. 

Small 33 

Smith,  C.  D.,  see  Fernald. 
Smith,  see  Coleman. 
Snell,  see  Atwater. 

Somermeier 230 

Stevenson 215 

Sundstrom 206 

Thompson 238 

Tutwiler 162 

U.  S.  Geological  Survey 173,  246 

U.  S.  Weather  Bureau 107 

White 51,  73,  84,  166 

White  and  Campbell 16,  42 

Winkler..  51 


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JUN  12  1950 


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